1 Introduction

GNU Guix1 is a functional
package management tool for the GNU system. Package management consists
of all activities that relate to building packages from sources,
honoring their build-time and run-time dependencies,
installing packages in user environments, upgrading installed packages
to new versions or rolling back to a previous set, removing unused
software packages, etc.

The term functional refers to a specific package management
discipline. In Guix, the package build and installation process is seen
as a function, in the mathematical sense. That function takes inputs,
such as build scripts, a compiler, and libraries, and
returns an installed package. As a pure function, its result depends
solely on its inputs—for instance, it cannot refer to software or
scripts that were not explicitly passed as inputs. A build function
always produces the same result when passed a given set of inputs. It
cannot alter the system’s environment in
any way; for instance, it cannot create, modify, or delete files outside
of its build and installation directories. This is achieved by running
build processes in isolated environments (or containers), where only their
explicit inputs are visible.

The result of package build functions is cached in the file
system, in a special directory called the store (see The Store). Each package is installed in a directory of its own, in the
store—by default under /gnu/store. The directory name contains
a hash of all the inputs used to build that package; thus, changing an
input yields a different directory name.

This approach is the foundation of Guix’s salient features: support for
transactional package upgrade and rollback, per-user installation, and
garbage collection of packages (see Features).

Guix has a command-line interface, which allows users to build, install,
upgrade, and remove packages, as well as a Scheme programming interface.

Last but not least, Guix is used to build a distribution of the GNU
system, with many GNU and non-GNU free software packages. The Guix
System Distribution, or GNU GuixSD, takes advantage of the core
properties of Guix at the system level. With GuixSD, users
declare all aspects of the operating system configuration, and
Guix takes care of instantiating that configuration in a reproducible,
stateless fashion. See GNU Distribution.

2 Installation

GNU Guix is available for download from its website at
http://www.gnu.org/software/guix/. This section describes the
software requirements of Guix, as well as how to install it and get
ready to use it.

Note that this section is concerned with the installation of the package
manager, which can be done on top of a running GNU/Linux system. If,
instead, you want to install the complete GNU operating system,
see System Installation.

2.1 Binary Installation

This section describes how to install Guix on an arbitrary system from a
self-contained tarball providing binaries for Guix and for all its
dependencies. This is often quicker than installing from source, which
is described in the next sections. The only requirement is to have
GNU tar and Xz.

Installing goes along these lines:

Download the binary tarball from
‘ftp://alpha.gnu.org/gnu/guix/guix-binary-0.8.3.system.tar.xz’2, where system
is x86_64-linux for an x86_64 machine already running the
kernel Linux, and so on.

2.2 Requirements

This section lists requirements when building Guix from source. The
build procedure for Guix is the same as for other GNU software, and is
not covered here. Please see the files README and INSTALL
in the Guix source tree for additional details.

When a working installation of the Nix package
manager is available, you
can instead configure Guix with --disable-daemon. In that case,
Nix replaces the three dependencies above.

Guix is compatible with Nix, so it is possible to share the same store
between both. To do so, you must pass configure not only the
same --with-store-dir value, but also the same
--localstatedir value. The latter is essential because it
specifies where the database that stores metadata about the store is
located, among other things. The default values for Nix are
--with-store-dir=/nix/store and --localstatedir=/nix/var.
Note that --disable-daemon is not required if
your goal is to share the store with Nix.

2.3 Running the Test Suite

After a successful configure and make run, it is a good
idea to run the test suite. It can help catch issues with the setup or
environment, or bugs in Guix itself—and really, reporting test
failures is a good way to help improve the software. To run the test
suite, type:

make check

Test cases can run in parallel: you can use the -j option of
GNU make to speed things up. The first run may take a few minutes
on a recent machine; subsequent runs will be faster because the store
that is created for test purposes will already have various things in
cache.

Upon failure, please email bug-guix@gnu.org and attach the
test-suite.log file. When tests/something.scm
fails, please also attach the something.log file available
in the top-level build directory. Please specify the Guix version being
used as well as version numbers of the dependencies
(see Requirements) in your message.

2.4 Setting Up the Daemon

Operations such as building a package or running the garbage collector
are all performed by a specialized process, the build daemon, on
behalf of clients. Only the daemon may access the store and its
associated database. Thus, any operation that manipulates the store
goes through the daemon. For instance, command-line tools such as
guix package and guix build communicate with the
daemon (via remote procedure calls) to instruct it what to do.

The following sections explain how to prepare the build daemon’s
environment. Also Substitutes, for information on how to allow
the daemon to download pre-built binaries.

2.4.1 Build Environment Setup

In a standard multi-user setup, Guix and its daemon—the
guix-daemon program—are installed by the system
administrator; /gnu/store is owned by root and
guix-daemon runs as root. Unprivileged users may use
Guix tools to build packages or otherwise access the store, and the
daemon will do it on their behalf, ensuring that the store is kept in a
consistent state, and allowing built packages to be shared among users.

When guix-daemon runs as root, you may not want package
build processes themselves to run as root too, for obvious
security reasons. To avoid that, a special pool of build users
should be created for use by build processes started by the daemon.
These build users need not have a shell and a home directory: they will
just be used when the daemon drops root privileges in build
processes. Having several such users allows the daemon to launch
distinct build processes under separate UIDs, which guarantees that they
do not interfere with each other—an essential feature since builds are
regarded as pure functions (see Introduction).

On a GNU/Linux system, a build user pool may be created like this (using
Bash syntax and the shadow commands):

The number of build users determines how many build jobs may run in
parallel, as specified by the --max-jobs option
(see --max-jobs). The
guix-daemon program may then be run as root with the
following command3:

# guix-daemon --build-users-group=guixbuild

This way, the daemon starts build processes in a chroot, under one of
the guixbuilder users. On GNU/Linux, by default, the chroot
environment contains nothing but:

a minimal /dev directory, created mostly independently from the
host /dev4;

the /proc directory; it only shows the container’s processes
since a separate PID name space is used;

/etc/passwd with an entry for the current user and an entry for
user nobody;

/etc/group with an entry for the user’s group;

/etc/hosts with an entry that maps localhost to
127.0.0.1;

a writable /tmp directory.

If you are installing Guix as an unprivileged user, it is still possible
to run guix-daemon provided you pass --disable-chroot.
However, build processes will not be isolated from one another, and not
from the rest of the system. Thus, build processes may interfere with
each other, and may access programs, libraries, and other files
available on the system—making it much harder to view them as
pure functions.

2.4.2 Using the Offload Facility

When desired, the build daemon can offload
derivation builds to other machines
running Guix, using the offloadbuild hook. When that
feature is enabled, a list of user-specified build machines is read from
/etc/guix/machines.scm; anytime a build is requested, for
instance via guix build, the daemon attempts to offload it to one
of the machines that satisfies the derivation’s constraints, in
particular its system type—e.g., x86_64-linux. Missing
prerequisites for the build are copied over SSH to the target machine,
which then proceeds with the build; upon success the output(s) of the
build are copied back to the initial machine.

In the example above we specify a list of two build machines, one for
the x86_64 architecture and one for the mips64el
architecture.

In fact, this file is—not surprisingly!—a Scheme file that is
evaluated when the offload hook is started. Its return value
must be a list of build-machine objects. While this example
shows a fixed list of build machines, one could imagine, say, using
DNS-SD to return a list of potential build machines discovered in the
local network (see Guile-Avahi in Using
Avahi in Guile Scheme Programs). The build-machine data type is
detailed below.

Data Type: build-machine

This data type represents build machines the daemon may offload builds
to. The important fields are:

name

The remote machine’s host name.

system

The remote machine’s system type—e.g., "x86_64-linux".

user

The user account to use when connecting to the remote machine over SSH.
Note that the SSH key pair must not be passphrase-protected, to
allow non-interactive logins.

A number of optional fields may be specified:

port

Port number of the machine’s SSH server (default: 22).

private-key

The SSH private key file to use when connecting to the machine.

Currently offloading uses GNU lsh as its SSH client
(see (GNU lsh Manual)Invoking lsh). Thus, the key file here must
be an lsh key file. This may change in the future, though.

parallel-builds

The number of builds that may run in parallel on the machine (1 by
default.)

speed

A “relative speed factor”. The offload scheduler will tend to prefer
machines with a higher speed factor.

features

A list of strings denoting specific features supported by the machine.
An example is "kvm" for machines that have the KVM Linux modules
and corresponding hardware support. Derivations can request features by
name, and they will be scheduled on matching build machines.

The guix command must be in the search path on the build
machines, since offloading works by invoking the guix archive and
guix build commands. In addition, the Guix modules must be in
$GUILE_LOAD_PATH on the build machine—you can check whether
this is the case by running:

lsh build-machine guile -c '(use-modules (guix config))'

There’s one last thing to do once machines.scm is in place. As
explained above, when offloading, files are transferred back and forth
between the machine stores. For this to work, you first need to
generate a key pair on each machine to allow the daemon to export signed
archives of files from the store (see Invoking guix archive):

# guix archive --generate-key

Each build machine must authorize the key of the master machine so that
it accepts store items it receives from the master:

# guix archive --authorize < master-public-key.txt

Likewise, the master machine must authorize the key of each build machine.

All the fuss with keys is here to express pairwise mutual trust
relations between the master and the build machines. Concretely, when
the master receives files from a build machine (and vice versa), its
build daemon can make sure they are genuine, have not been tampered
with, and that they are signed by an authorized key.

2.5 Invoking guix-daemon

The guix-daemon program implements all the functionality to
access the store. This includes launching build processes, running the
garbage collector, querying the availability of a build result, etc. It
is normally run as root like this:

By default, guix-daemon launches build processes under
different UIDs, taken from the build group specified with
--build-users-group. In addition, each build process is run in a
chroot environment that only contains the subset of the store that the
build process depends on, as specified by its derivation
(see derivation), plus a set of specific
system directories. By default, the latter contains /dev and
/dev/pts. Furthermore, on GNU/Linux, the build environment is a
container: in addition to having its own file system tree, it has
a separate mount name space, its own PID name space, network name space,
etc. This helps achieve reproducible builds (see Features).

When the daemon performs a build on behalf of the user, it creates a
build directory under /tmp or under the directory specified by
its TMPDIR environment variable; this directory is shared with
the container for the duration of the build. Be aware that using a
directory other than /tmp can affect build results—for example,
with a longer directory name, a build process that uses Unix-domain
sockets might hit the name length limitation for sun_path, which
it would otherwise not hit.

The build directory is automatically deleted upon completion, unless the
build failed and the client specified --keep-failed
(see --keep-failed).

Do not use substitutes for build products. That is, always build things
locally instead of allowing downloads of pre-built binaries
(see Substitutes).

By default substitutes are used, unless the client—such as the
guix package command—is explicitly invoked with
--no-substitutes.

When the daemon runs with --no-substitutes, clients can still
explicitly enable substitution via the set-build-options
remote procedure call (see The Store).

--substitute-urls=urls

Consider urls the default whitespace-separated list of substitute
source URLs. When this option is omitted, ‘http://hydra.gnu.org’
is used.

This means that substitutes may be downloaded from urls, as long
as they are signed by a trusted signature (see Substitutes).

--no-build-hook

Do not use the build hook.

The build hook is a helper program that the daemon can start and to
which it submits build requests. This mechanism is used to offload
builds to other machines (see Daemon Offload Setup).

--cache-failures

Cache build failures. By default, only successful builds are cached.

--cores=n

-c n

Use n CPU cores to build each derivation; 0 means as many
as available.

The default value is 0, but it may be overridden by clients, such
as the --cores option of guix build (see Invoking guix build).

The effect is to define the NIX_BUILD_CORES environment variable
in the build process, which can then use it to exploit internal
parallelism—for instance, by running make -j$NIX_BUILD_CORES.

--max-jobs=n

-M n

Allow at most n build jobs in parallel. The default value is
1. Setting it to 0 means that no builds will be performed
locally; instead, the daemon will offload builds (see Daemon Offload Setup), or simply fail.

--debug

Produce debugging output.

This is useful to debug daemon start-up issues, but then it may be
overridden by clients, for example the --verbosity option of
guix build (see Invoking guix build).

--chroot-directory=dir

Add dir to the build chroot.

Doing this may change the result of build processes—for instance if
they use optional dependencies found in dir when it is available,
and not otherwise. For that reason, it is not recommended to do so.
Instead, make sure that each derivation declares all the inputs that it
needs.

--disable-chroot

Disable chroot builds.

Using this option is not recommended since, again, it would allow build
processes to gain access to undeclared dependencies. It is necessary,
though, when guix-daemon is running under an unprivileged user
account.

--disable-log-compression

Disable compression of the build logs.

Unless --lose-logs is used, all the build logs are kept in the
localstatedir. To save space, the daemon automatically compresses
them with bzip2 by default. This option disables that.

--disable-deduplication

Disable automatic file “deduplication” in the store.

By default, files added to the store are automatically “deduplicated”:
if a newly added file is identical to another one found in the store,
the daemon makes the new file a hard link to the other file. This can
noticeably reduce disk usage, at the expense of slightly increasde
input/output load at the end of a build process. This option disables
this optimization.

--gc-keep-outputs[=yes|no]

Tell whether the garbage collector (GC) must keep outputs of live
derivations.

When set to “yes”, the GC will keep the outputs of any live derivation
available in the store—the .drv files. The default is “no”,
meaning that derivation outputs are kept only if they are GC roots.

--gc-keep-derivations[=yes|no]

Tell whether the garbage collector (GC) must keep derivations
corresponding to live outputs.

When set to “yes”, as is the case by default, the GC keeps
derivations—i.e., .drv files—as long as at least one of their
outputs is live. This allows users to keep track of the origins of
items in their store. Setting it to “no” saves a bit of disk space.

Note that when both --gc-keep-derivations and
--gc-keep-outputs are used, the effect is to keep all the build
prerequisites (the sources, compiler, libraries, and other build-time
tools) of live objects in the store, regardless of whether these
prerequisites are live. This is convenient for developers since it
saves rebuilds or downloads.

--impersonate-linux-2.6

On Linux-based systems, impersonate Linux 2.6. This means that the
kernel’s uname system call will report 2.6 as the release number.

This might be helpful to build programs that (usually wrongfully) depend
on the kernel version number.

--lose-logs

Do not keep build logs. By default they are kept under
localstatedir/guix/log.

--system=system

Assume system as the current system type. By default it is the
architecture/kernel pair found at configure time, such as
x86_64-linux.

--listen=socket

Listen for connections on socket, the file name of a Unix-domain
socket. The default socket is
localstatedir/daemon-socket/socket. This option is only
useful in exceptional circumstances, such as if you need to run several
daemons on the same machine.

2.6 Application Setup

When using Guix on top of GNU/Linux distribution other than GuixSD, a
few additional steps are needed to get everything in place. Here are
some of them.

2.6.1 Locales

Packages installed via Guix will not use the host system’s locale
data. Instead, you must first install one of the locale packages
available with Guix and then define the LOCPATH environment
variable (see LOCPATH in The GNU C Library
Reference Manual):

Note that the glibc-locales package contains data for all the
locales supported by the GNU libc and weighs in at around
110 MiB. Alternately, the glibc-utf8-locales is smaller but
limited to a few UTF-8 locales.

2.6.2 X11 Fonts

The majority of graphical applications uses Fontconfig to locate and
load fonts and perform X11-client-side rendering. Guix’s
fontconfig package looks for fonts in $HOME/.guix-profile
by default. Thus, to allow graphical applications installed with Guix
to display fonts, you will have to install fonts with Guix as well.
Essential font packages include gs-fonts, font-dejavu, and
font-gnu-freefont.

3 Package Management

The purpose of GNU Guix is to allow users to easily install, upgrade, and
remove software packages, without having to know about their build
procedure or dependencies. Guix also goes beyond this obvious set of
features.

This chapter describes the main features of Guix, as well as the package
management tools it provides. Two user interfaces are provided for
routine package management tasks: a command-line interface
(see guix package), and a visual user
interface in Emacs (see Emacs Interface).

3.1 Features

When using Guix, each package ends up in the package store, in its
own directory—something that resembles
/gnu/store/xxx-package-1.2, where xxx is a base32 string
(note that Guix comes with an Emacs extension to shorten those file
names, see Emacs Prettify.)

Instead of referring to these directories, users have their own
profile, which points to the packages that they actually want to
use. These profiles are stored within each user’s home directory, at
$HOME/.guix-profile.

For example, alice installs GCC 4.7.2. As a result,
/home/alice/.guix-profile/bin/gcc points to
/gnu/store/…-gcc-4.7.2/bin/gcc. Now, on the same machine,
bob had already installed GCC 4.8.0. The profile of bob
simply continues to point to
/gnu/store/…-gcc-4.8.0/bin/gcc—i.e., both versions of GCC
coexist on the same system without any interference.

The guix package command is the central tool to manage
packages (see Invoking guix package). It operates on those per-user
profiles, and can be used with normal user privileges.

The command provides the obvious install, remove, and upgrade
operations. Each invocation is actually a transaction: either
the specified operation succeeds, or nothing happens. Thus, if the
guix package process is terminated during the transaction,
or if a power outage occurs during the transaction, then the user’s
profile remains in its previous state, and remains usable.

In addition, any package transaction may be rolled back. So, if,
for example, an upgrade installs a new version of a package that turns
out to have a serious bug, users may roll back to the previous instance
of their profile, which was known to work well. Similarly, the global
system configuration is subject to transactional upgrades and roll-back
(see Using the Configuration System).

All those packages in the package store may be garbage-collected.
Guix can determine which packages are still referenced by the user
profiles, and remove those that are provably no longer referenced
(see Invoking guix gc). Users may also explicitly remove old
generations of their profile so that the packages they refer to can be
collected.

Finally, Guix takes a purely functional approach to package
management, as described in the introduction (see Introduction).
Each /gnu/store package directory name contains a hash of all the
inputs that were used to build that package—compiler, libraries, build
scripts, etc. This direct correspondence allows users to make sure a
given package installation matches the current state of their
distribution. It also helps maximize build reproducibility:
thanks to the isolated build environments that are used, a given build
is likely to yield bit-identical files when performed on different
machines (see container).

This foundation allows Guix to support transparent binary/source
deployment. When a pre-built binary for a /gnu/store item is
available from an external source—a substitute, Guix just
downloads it and unpacks it;
otherwise, it builds the package from source, locally
(see Substitutes).

Control over the build environment is a feature that is also useful for
developers. The guix environment command allows developers of
a package to quickly set up the right development environment for their
package, without having to manually install the package’s dependencies
in their profile (see Invoking guix environment).

3.2 Invoking guix package

The guix package command is the tool that allows users to
install, upgrade, and remove packages, as well as rolling back to
previous configurations. It operates only on the user’s own profile,
and works with normal user privileges (see Features). Its syntax
is:

guix package options

Primarily, options specifies the operations to be performed during
the transaction. Upon completion, a new profile is created, but
previous generations of the profile remain available, should the user
want to roll back.

For example, to remove lua and install guile and
guile-cairo in a single transaction:

guix package -r lua -i guile guile-cairo

guix package also supports a declarative approach
whereby the user specifies the exact set of packages to be available and
passes it via the --manifest option
(see --manifest).

For each user, a symlink to the user’s default profile is automatically
created in $HOME/.guix-profile. This symlink always points to the
current generation of the user’s default profile. Thus, users can add
$HOME/.guix-profile/bin to their PATH environment
variable, and so on.
If you are not using the Guix System Distribution, consider adding the
following lines to your ~/.bash_profile (see Bash Startup
Files in The GNU Bash Reference Manual) so that newly-spawned
shells get all the right environment variable definitions:

In a multi-user setup, user profiles are stored in a place registered as
a garbage-collector root, which $HOME/.guix-profile points
to (see Invoking guix gc). That directory is normally
localstatedir/profiles/per-user/user, where
localstatedir is the value passed to configure as
--localstatedir, and user is the user name. The
per-user directory is created when guix-daemon is
started, and the user sub-directory is created by guix
package.

The options can be among the following:

--install=package …

-i package …

Install the specified packages.

Each package may specify either a simple package name, such as
guile, or a package name followed by a hyphen and version number,
such as guile-1.8.8 or simply guile-1.8 (in the latter
case, the newest version prefixed by 1.8 is selected.)

If no version number is specified, the
newest available version will be selected. In addition, package
may contain a colon, followed by the name of one of the outputs of the
package, as in gcc:doc or binutils-2.22:lib
(see Packages with Multiple Outputs). Packages with a corresponding
name (and optionally version) are searched for among the GNU
distribution modules (see Package Modules).

Sometimes packages have propagated inputs: these are dependencies
that automatically get installed along with the required package
(see propagated-inputs in
package objects, for information about propagated inputs in
package definitions).

An example is the GNU MPC library: its C header files refer to those of
the GNU MPFR library, which in turn refer to those of the GMP library.
Thus, when installing MPC, the MPFR and GMP libraries also get installed
in the profile; removing MPC also removes MPFR and GMP—unless they had
also been explicitly installed independently.

Besides, packages sometimes rely on the definition of environment
variables for their search paths (see explanation of
--search-paths below). Any missing or possibly incorrect
environment variable definitions are reported here.

Finally, when installing a GNU package, the tool reports the
availability of a newer upstream version. In the future, it may provide
the option of installing directly from the upstream version, even if
that version is not yet in the distribution.

--install-from-expression=exp

-e exp

Install the package exp evaluates to.

exp must be a Scheme expression that evaluates to a
<package> object. This option is notably useful to disambiguate
between same-named variants of a package, with expressions such as
(@ (gnu packages base) guile-final).

Note that this option installs the first output of the specified
package, which may be insufficient when needing a specific output of a
multiple-output package.

--remove=package …

-r package …

Remove the specified packages.

As for --install, each package may specify a version number
and/or output name in addition to the package name. For instance,
-r glibc:debug would remove the debug output of
glibc.

--upgrade[=regexp …]

-u [regexp …]

Upgrade all the installed packages. If one or more regexps are
specified, upgrade only installed packages whose name matches a
regexp. Also see the --do-not-upgrade option below.

Note that this upgrades package to the latest version of packages found
in the distribution currently installed. To update your distribution,
you should regularly run guix pull (see Invoking guix pull).

--do-not-upgrade[=regexp …]

When used together with the --upgrade option, do not
upgrade any packages whose name matches a regexp. For example, to
upgrade all packages in the current profile except those containing the
substring “emacs”:

$ guix package --upgrade . --do-not-upgrade emacs

--manifest=file

-m file

Create a new generation of the profile from the manifest object
returned by the Scheme code in file.

This allows you to declare the profile’s contents rather than
constructing it through a sequence of --install and similar
commands. The advantage is that file can be put under version
control, copied to different machines to reproduce the same profile, and
so on.

file must return a manifest object, which is roughly a list
of packages:

Roll back to the previous generation of the profile—i.e., undo
the last transaction.

When combined with options such as --install, roll back occurs
before any other actions.

When rolling back from the first generation that actually contains
installed packages, the profile is made to point to the zeroth
generation, which contains no files apart from its own meta-data.

Installing, removing, or upgrading packages from a generation that has
been rolled back to overwrites previous future generations. Thus, the
history of a profile’s generations is always linear.

--switch-generation=pattern

-S pattern

Switch to a particular generation defined by pattern.

pattern may be either a generation number or a number prefixed
with “+” or “-”. The latter means: move forward/backward by a
specified number of generations. For example, if you want to return to
the latest generation after --roll-back, use
--switch-generation=+1.

The difference between --roll-back and
--switch-generation=-1 is that --switch-generation will
not make a zeroth generation, so if a specified generation does not
exist, the current generation will not be changed.

--search-paths[=kind]

Report environment variable definitions, in Bash syntax, that may be
needed in order to use the set of installed packages. These environment
variables are used to specify search paths for files used by some
of the installed packages.

For example, GCC needs the CPATH and LIBRARY_PATH
environment variables to be defined so it can look for headers and
libraries in the user’s profile (see Environment Variables in Using the GNU Compiler Collection (GCC)). If GCC and, say, the C
library are installed in the profile, then --search-paths will
suggest setting these variables to profile/include and
profile/lib, respectively.

The typical use case is to define these environment variables in the
shell:

$ eval `guix package --search-paths`

kind may be one of exact, prefix, or suffix,
meaning that the returned environment variable definitions will either
be exact settings, or prefixes or suffixes of the current value of these
variables. When omitted, kind defaults to exact.

List the currently installed packages in the specified profile, with the
most recently installed packages shown last. When regexp is
specified, list only installed packages whose name matches regexp.

For each installed package, print the following items, separated by
tabs: the package name, its version string, the part of the package that
is installed (for instance, out for the default output,
include for its headers, etc.), and the path of this package in
the store.

--list-available[=regexp]

-A [regexp]

List packages currently available in the distribution for this system
(see GNU Distribution). When regexp is specified, list only
installed packages whose name matches regexp.

For each package, print the following items separated by tabs: its name,
its version string, the parts of the package (see Packages with Multiple Outputs), and the source location of its definition.

--list-generations[=pattern]

-l [pattern]

Return a list of generations along with their creation dates; for each
generation, show the installed packages, with the most recently
installed packages shown last. Note that the zeroth generation is never
shown.

For each installed package, print the following items, separated by
tabs: the name of a package, its version string, the part of the package
that is installed (see Packages with Multiple Outputs), and the
location of this package in the store.

When pattern is used, the command returns only matching
generations. Valid patterns include:

Integers and comma-separated integers. Both patterns denote
generation numbers. For instance, --list-generations=1 returns
the first one.

And --list-generations=1,8,2 outputs three generations in the
specified order. Neither spaces nor trailing commas are allowed.

Ranges. --list-generations=2..9 prints the
specified generations and everything in between. Note that the start of
a range must be lesser than its end.

It is also possible to omit the endpoint. For example,
--list-generations=2.., returns all generations starting from the
second one.

Durations. You can also get the last N days, weeks,
or months by passing an integer along with the first letter of the
duration. For example, --list-generations=20d lists generations
that are up to 20 days old.

--delete-generations[=pattern]

-d [pattern]

When pattern is omitted, delete all generations except the current
one.

This command accepts the same patterns as --list-generations.
When pattern is specified, delete the matching generations. When
pattern specifies a duration, generations older than the
specified duration match. For instance, --delete-generations=1m
deletes generations that are more than one month old.

If the current generation matches, it is not deleted. Also, the
zeroth generation is never deleted.

Note that deleting generations prevents roll-back to them.
Consequently, this command must be used with care.

Finally, since guix package may actually start build
processes, it supports all the common build options that guix
build supports (see common build options).

3.3 Emacs Interface

GNU Guix comes with a visual user interface for GNU Emacs, known
as “guix.el”. It can be used for routine package management tasks,
pretty much like the guix package command (see Invoking guix package). Specifically, “guix.el” makes it easy to:

3.3.1 Initial Setup

On the Guix System Distribution (see GNU Distribution), “guix.el”
is ready to use, provided Guix is installed system-wide, which is the
case by default. So if that is what you’re using, you can happily skip
this section and read about the fun stuff.

If you’re not yet a happy user of GuixSD, a little bit of setup is needed.
To be able to use “guix.el”, you need to install the following
packages:

So the only thing you need to figure out is where the directory with
elisp files for Guix is placed. It depends on how you installed Guix:

If it was installed by a package manager of your distribution or by a
usual ./configure && make && make install command sequence, then
elisp files are placed in a standard directory with Emacs packages
(usually it is /usr/share/emacs/site-lisp/), which is already in
load-path, so there is no need to add that directory there.

If you used a binary installation method (see Binary Installation),
then Guix is installed somewhere in the store, so the elisp files are
placed in /gnu/store/…-guix-0.8.2/share/emacs/site-lisp/ or
alike. However it is not recommended to refer directly to a store
directory. Instead you can install Guix using Guix itself with
guix package -i guix command (see Invoking guix package)
and add ~/.guix-profile/share/emacs/site-lisp/ directory to
load-path variable.

If you did not install Guix at all and prefer a hacking way
(see Running Guix Before It Is Installed), along with augmenting
load-path you need to set guix-load-path variable to the
same directory, so your final configuration will look like this:

By default, along with autoloading (see Autoload in The GNU
Emacs Lisp Reference Manual) the main interactive commands for
“guix.el” (see Emacs Commands), requiring guix-init will
also autoload commands for the Emacs packages installed in your user
profile.

To disable automatic loading of installed Emacs packages, set
guix-package-enable-at-startup variable to nil before
requiring guix-init. This variable has the same meaning for
Emacs packages installed with Guix, as package-enable-at-startup
for the built-in Emacs package system (see Package Installation in The GNU Emacs Manual).

You can activate Emacs packages installed in your profile whenever you
want using M-x guix-emacs-load-autoloads.

3.3.2.1 Commands

All commands for displaying packages and generations use the current
profile, which can be changed with
M-x guix-set-current-profile. Alternatively, if you call any
of these commands with prefix argument (C-u), you will be prompted
for a profile just for that command.

Commands for displaying packages:

M-x guix-all-available-packages

M-x guix-newest-available-packages

Display all/newest available packages.

M-x guix-installed-packages

Display all installed packages.

M-x guix-obsolete-packages

Display obsolete packages (the packages that are installed in a profile
but cannot be found among available packages).

M-x guix-search-by-name

Display package(s) with the specified name.

M-x guix-search-by-regexp

Search for packages by a specified regexp. By default “name”,
“synopsis” and “description” of the packages will be searched. This
can be changed by modifying guix-search-params variable.

By default, these commands display each output on a separate line. If
you prefer to see a list of packages—i.e., a list with a package per
line, use the following setting:

(setq guix-package-list-type 'package)

Commands for displaying generations:

M-x guix-generations

List all the generations.

M-x guix-last-generations

List the N last generations. You will be prompted for the number
of generations.

M-x guix-generations-by-time

List generations matching time period. You will be prompted for the
period using Org mode time prompt based on Emacs calendar (see The
date/time prompt in The Org Manual).

Hint: If you need several “list” or “info” buffers, you can
simlpy M-x clone-buffer them, and each buffer will have its own
history.

Warning: Name/version pairs cannot be used to identify packages
(because a name is not necessarily unique), so “guix.el” uses special
identifiers that live only during a guile session, so if the Guix REPL
was restarted, you may want to revert “list” buffer (by pressing
g).

3.3.3 Configuration

There are many variables you can modify to change the appearance or
behavior of Emacs user interface. Some of these variables are described
in this section. Also you can use Custom Interface (see Easy
Customization in The GNU Emacs Manual) to explore/set variables
(not all) and faces.

3.4 Substitutes

Guix supports transparent source/binary deployment, which means that it
can either build things locally, or download pre-built items from a
server. We call these pre-built items substitutes—they are
substitutes for local build results. In many cases, downloading a
substitute is much faster than building things locally.

Substitutes can be anything resulting from a derivation build
(see Derivations). Of course, in the common case, they are
pre-built package binaries, but source tarballs, for instance, which
also result from derivation builds, can be available as substitutes.

The hydra.gnu.org server is a front-end to a build farm that
builds packages from the GNU distribution continuously for some
architectures, and makes them available as substitutes. This is the
default source of substitutes; it can be overridden by passing the
--substitute-urls option either to guix-daemon
(see guix-daemon --substitute-urls)
or to client tools such as guix package
(see client --substitute-urls
option).

To allow Guix to download substitutes from hydra.gnu.org, you
must add its public key to the access control list (ACL) of archive
imports, using the guix archive command (see Invoking guix archive). Doing so implies that you trust hydra.gnu.org to not
be compromised and to serve genuine substitutes.

This public key is installed along with Guix, in
prefix/share/guix/hydra.gnu.org.pub, where prefix is
the installation prefix of Guix. If you installed Guix from source,
make sure you checked the GPG signature of
guix-0.8.3.tar.gz, which contains this public key file.
Then, you can run something like this:

# guix archive --authorize < hydra.gnu.org.pub

Once this is in place, the output of a command like guix build
should change from something like:

This indicates that substitutes from hydra.gnu.org are usable and
will be downloaded, when possible, for future builds.

Guix ignores substitutes that are not signed, or that are not signed by
one of the keys listed in the ACL. It also detects and raises an error
when attempting to use a substitute that has been tampered with.

The substitute mechanism can be disabled globally by running
guix-daemon with --no-substitutes (see Invoking guix-daemon). It can also be disabled temporarily by passing the
--no-substitutes option to guix package, guix
build, and other command-line tools.

Today, each individual’s control over their own computing is at the
mercy of institutions, corporations, and groups with enough power and
determination to subvert the computing infrastructure and exploit its
weaknesses. While using hydra.gnu.org substitutes can be
convenient, we encourage users to also build on their own, or even run
their own build farm, such that hydra.gnu.org is less of an
interesting target. One way to help is by publishing the software you
build using guix publish so that others have one more choice
of server to download substitutes from (see Invoking guix publish).

Guix has the foundations to maximize build reproducibility
(see Features). In most cases, independent builds of a given
package or derivation should yield bit-identical results. Thus, through
a diverse set of independent package builds, we can strengthen the
integrity of our systems.

In the future, we want Guix to have support to publish and retrieve
binaries to/from other users, in a peer-to-peer fashion. If you would
like to discuss this project, join us on guix-devel@gnu.org.

3.5 Packages with Multiple Outputs

Often, packages defined in Guix have a single output—i.e., the
source package leads exactly one directory in the store. When running
guix package -i glibc, one installs the default output of the
GNU libc package; the default output is called out, but its name
can be omitted as shown in this command. In this particular case, the
default output of glibc contains all the C header files, shared
libraries, static libraries, Info documentation, and other supporting
files.

Sometimes it is more appropriate to separate the various types of files
produced from a single source package into separate outputs. For
instance, the GLib C library (used by GTK+ and related packages)
installs more than 20 MiB of reference documentation as HTML pages.
To save space for users who do not need it, the documentation goes to a
separate output, called doc. To install the main GLib output,
which contains everything but the documentation, one would run:

guix package -i glib

The command to install its documentation is:

guix package -i glib:doc

Some packages install programs with different “dependency footprints”.
For instance, the WordNet package install both command-line tools and
graphical user interfaces (GUIs). The former depend solely on the C
library, whereas the latter depend on Tcl/Tk and the underlying X
libraries. In this case, we leave the command-line tools in the default
output, whereas the GUIs are in a separate output. This allows users
who do not need the GUIs to save space. The guix size command
can help find out about such situations (see Invoking guix size).

There are several such multiple-output packages in the GNU distribution.
Other conventional output names include lib for libraries and
possibly header files, bin for stand-alone programs, and
debug for debugging information (see Installing Debugging Files). The outputs of a packages are listed in the third column of
the output of guix package --list-available (see Invoking guix package).

3.6 Invoking guix gc

Packages that are installed but not used may be garbage-collected.
The guix gc command allows users to explicitly run the garbage
collector to reclaim space from the /gnu/store directory. It is
the only way to remove files from /gnu/store—removing
files or directories manually may break it beyond repair!

The garbage collector has a set of known roots: any file under
/gnu/store reachable from a root is considered live and
cannot be deleted; any other file is considered dead and may be
deleted. The set of garbage collector roots includes default user
profiles, and may be augmented with guix build --root, for
example (see Invoking guix build).

Prior to running guix gc --collect-garbage to make space, it is
often useful to remove old generations from user profiles; that way, old
package builds referenced by those generations can be reclaimed. This
is achieved by running guix package --delete-generations
(see Invoking guix package).

The guix gc command has three modes of operation: it can be
used to garbage-collect any dead files (the default), to delete specific
files (the --delete option), to print garbage-collector
information, or for more advanced queries. The garbage collection
options are as follows:

--collect-garbage[=min]

-C [min]

Collect garbage—i.e., unreachable /gnu/store files and
sub-directories. This is the default operation when no option is
specified.

When min is given, stop once min bytes have been collected.
min may be a number of bytes, or it may include a unit as a
suffix, such as MiB for mebibytes and GB for gigabytes
(see size specifications in GNU Coreutils).

When min is omitted, collect all the garbage.

--delete

-d

Attempt to delete all the store files and directories specified as
arguments. This fails if some of the files are not in the store, or if
they are still live.

--list-dead

Show the list of dead files and directories still present in the
store—i.e., files and directories no longer reachable from any root.

--list-live

Show the list of live store files and directories.

In addition, the references among existing store files can be queried:

--references

--referrers

List the references (respectively, the referrers) of store files given
as arguments.

--requisites

-R

List the requisites of the store files passed as arguments. Requisites
include the store files themselves, their references, and the references
of these, recursively. In other words, the returned list is the
transitive closure of the store files.

Lastly, the following options allow you to check the integrity of the
store and to control disk usage.

--verify[=options]

Verify the integrity of the store.

By default, make sure that all the store items marked as valid in the
daemon’s database actually exist in /gnu/store.

When provided, options must a comma-separated list containing one
or more of contents and repair.

When passing --verify=contents, the daemon will compute the
content hash of each store item and compare it against its hash in the
database. Hash mismatches are reported as data corruptions. Because it
traverses all the files in the store, this command can take a
long time, especially on systems with a slow disk drive.

Using --verify=repair or --verify=contents,repair
causes the daemon to try to repair corrupt store items by fetching
substitutes for them (see Substitutes). Because repairing is not
atomic, and thus potentially dangerous, it is available only to the
system administrator.

--optimize

Optimize the store by hard-linking identical files—this is
deduplication.

The daemon performs deduplication after each successful build or archive
import, unless it was started with --disable-deduplication
(see --disable-deduplication). Thus,
this option is primarily useful when the daemon was running with
--disable-deduplication.

3.7 Invoking guix pull

Packages are installed or upgraded to the latest version available in
the distribution currently available on your local machine. To update
that distribution, along with the Guix tools, you must run guix
pull: the command downloads the latest Guix source code and package
descriptions, and deploys it.

On completion, guix package will use packages and package
versions from this just-retrieved copy of Guix. Not only that, but all
the Guix commands and Scheme modules will also be taken from that latest
version. New guix sub-commands added by the update also
become available.

The guix pull command is usually invoked with no arguments,
but it supports the following options:

3.8 Invoking guix archive

The guix archive command allows users to export files
from the store into a single archive, and to later import them.
In particular, it allows store files to be transferred from one machine
to another machine’s store. For example, to transfer the emacs
package to a machine connected over SSH, one would run:

However, note that, in both examples, all of emacs and the
profile as well as all of their dependencies are transferred (due to
-r), regardless of what is already available in the target
machine’s store. The --missing option can help figure out which
items are missing from the target’s store.

Archives are stored in the “Nix archive” or “Nar” format, which is
comparable in spirit to ‘tar’, but with a few noteworthy differences
that make it more appropriate for our purposes. First, rather than
recording all Unix meta-data for each file, the Nar format only mentions
the file type (regular, directory, or symbolic link); Unix permissions
and owner/group are dismissed. Second, the order in which directory
entries are stored always follows the order of file names according to
the C locale collation order. This makes archive production fully
deterministic.

When exporting, the daemon digitally signs the contents of the archive,
and that digital signature is appended. When importing, the daemon
verifies the signature and rejects the import in case of an invalid
signature or if the signing key is not authorized.

Dependencies are not included in the output, unless
--recursive is passed.

-r

--recursive

When combined with --export, this instructs guix
archive to include dependencies of the given items in the archive.
Thus, the resulting archive is self-contained: it contains the closure
of the exported store items.

--import

Read an archive from the standard input, and import the files listed
therein into the store. Abort if the archive has an invalid digital
signature, or if it is signed by a public key not among the authorized
keys (see --authorize below.)

--missing

Read a list of store file names from the standard input, one per line,
and write on the standard output the subset of these files missing from
the store.

--generate-key[=parameters]

Generate a new key pair for the daemons. This is a prerequisite before
archives can be exported with --export. Note that this operation
usually takes time, because it needs to gather enough entropy to
generate the key pair.

The generated key pair is typically stored under /etc/guix, in
signing-key.pub (public key) and signing-key.sec (private
key, which must be kept secret.) When parameters is omitted,
an ECDSA key using the Ed25519 curve is generated, or, for Libgcrypt
versions before 1.6.0, it is a 4096-bit RSA key.
Alternately, parameters can specify
genkey parameters suitable for Libgcrypt (see gcry_pk_genkey in The
Libgcrypt Reference Manual).

--authorize

Authorize imports signed by the public key passed on standard input.
The public key must be in “s-expression advanced format”—i.e., the
same format as the signing-key.pub file.

specifications may be either store file names or package
specifications, as for guix package (see Invoking guix package). For instance, the following command creates an archive
containing the gui output of the git package and the main
output of emacs:

guix archive --export git:gui /gnu/store/...-emacs-24.3 > great.nar

If the specified packages are not built yet, guix archive
automatically builds them. The build process may be controlled with the
same options that can be passed to the guix build command
(see common build options).

4 Programming Interface

GNU Guix provides several Scheme programming interfaces (APIs) to
define, build, and query packages. The first interface allows users to
write high-level package definitions. These definitions refer to
familiar packaging concepts, such as the name and version of a package,
its build system, and its dependencies. These definitions can then be
turned into concrete build actions.

Build actions are performed by the Guix daemon, on behalf of users. In a
standard setup, the daemon has write access to the store—the
/gnu/store directory—whereas users do not. The recommended
setup also has the daemon perform builds in chroots, under a specific
build users, to minimize interference with the rest of the system.

Lower-level APIs are available to interact with the daemon and the
store. To instruct the daemon to perform a build action, users actually
provide it with a derivation. A derivation is a low-level
representation of the build actions to be taken, and the environment in
which they should occur—derivations are to package definitions what
assembly is to C programs. The term “derivation” comes from the fact
that build results derive from them.

This chapter describes all these APIs in turn, starting from high-level
package definitions.

4.1 Defining Packages

The high-level interface to package definitions is implemented in the
(guix packages) and (guix build-system) modules. As an
example, the package definition, or recipe, for the GNU Hello
package looks like this:

Without being a Scheme expert, the reader may have guessed the meaning
of the various fields here. This expression binds variable hello
to a <package> object, which is essentially a record
(see Scheme records in GNU Guile Reference Manual).
This package object can be inspected using procedures found in the
(guix packages) module; for instance, (package-name hello)
returns—surprise!—"hello".

With luck, you may be able to import part or all of the definition of
the package you are interested in from another repository, using the
guix import command (see Invoking guix import).

In the example above, hello is defined into a module of its own,
(gnu packages hello). Technically, this is not strictly
necessary, but it is convenient to do so: all the packages defined in
modules under (gnu packages …) are automatically known to
the command-line tools (see Package Modules).

There are a few points worth noting in the above package definition:

The source field of the package is an <origin> object
(see origin Reference, for the complete reference).
Here, the url-fetch method from (guix download) is used,
meaning that the source is a file to be downloaded over FTP or HTTP.

The mirror://gnu prefix instructs url-fetch to use one of
the GNU mirrors defined in (guix download).

The sha256 field specifies the expected SHA256 hash of the file
being downloaded. It is mandatory, and allows Guix to check the
integrity of the file. The (base32 …) form introduces the
base32 representation of the hash. You can obtain this information with
guix download (see Invoking guix download) and guix
hash (see Invoking guix hash).

When needed, the origin form can also have a patches field
listing patches to be applied, and a snippet field giving a
Scheme expression to modify the source code.

The build-system field specifies the procedure to build the
package (see Build Systems). Here, gnu-build-system
represents the familiar GNU Build System, where packages may be
configured, built, and installed with the usual ./configure &&
make && make check && make install command sequence.

The arguments field specifies options for the build system
(see Build Systems). Here it is interpreted by
gnu-build-system as a request run configure with the
--enable-silent-rules flag.

The inputs field specifies inputs to the build process—i.e.,
build-time or run-time dependencies of the package. Here, we define an
input called "gawk" whose value is that of the gawk
variable; gawk is itself bound to a <package> object.

Note that GCC, Coreutils, Bash, and other essential tools do not need to
be specified as inputs here. Instead, gnu-build-system takes care
of ensuring that they are present (see Build Systems).

However, any other dependencies need to be specified in the
inputs field. Any dependency not specified here will simply be
unavailable to the build process, possibly leading to a build failure.

Once a package definition is in place, the
package may actually be built using the guix build command-line
tool (see Invoking guix build). You can easily jump back to the
package definition using the guix edit command
(see Invoking guix edit).
See Packaging Guidelines, for
more information on how to test package definitions, and
Invoking guix lint, for information on how to check a definition
for style conformance.

Eventually, updating the package definition to a new upstream version
can be partly automated by the guix refresh command
(see Invoking guix refresh).

Behind the scenes, a derivation corresponding to the <package>
object is first computed by the package-derivation procedure.
That derivation is stored in a .drv file under /gnu/store.
The build actions it prescribes may then be realized by using the
build-derivations procedure (see The Store).

Scheme Procedure: package-derivationstorepackage [system]

Return the <derivation> object of package for system
(see Derivations).

package must be a valid <package> object, and system
must be a string denoting the target system type—e.g.,
"x86_64-linux" for an x86_64 Linux-based GNU system. store
must be a connection to the daemon, which operates on the store
(see The Store).

Similarly, it is possible to compute a derivation that cross-builds a
package for some other system:

Scheme Procedure: package-cross-derivationstorepackagetarget [system]

Return the <derivation> object of package cross-built from
system to target.

target must be a valid GNU triplet denoting the target hardware
and operating system, such as "mips64el-linux-gnu"
(see GNU configuration triplets in GNU
Configure and Build System).

4.1.1 package Reference

This section summarizes all the options available in package
declarations (see Defining Packages).

Data Type: package

This is the data type representing a package recipe.

name

The name of the package, as a string.

version

The version of the package, as a string.

source

An origin object telling how the source code for the package should be
acquired (see origin Reference).

build-system

The build system that should be used to build the package (see Build Systems).

arguments (default: '())

The arguments that should be passed to the build system. This is a
list, typically containing sequential keyword-value pairs.

inputs (default: '())

Package or derivation inputs to the build. This is a list of lists,
where each list has the name of the input (a string) as its first
element, a package or derivation object as its second element, and
optionally the name of the output of the package or derivation that
should be used, which defaults to "out".

propagated-inputs (default: '())

This field is like inputs, but the specified packages will be
force-installed alongside the package they belong to
(see guix package, for
information on how guix package deals with propagated inputs.)

For example this is necessary when a library needs headers of another
library to compile, or needs another shared library to be linked
alongside itself when a program wants to link to it.

native-inputs (default: '())

This field is like inputs, but in case of a cross-compilation it
will be ensured that packages for the architecture of the build machine
are present, such that executables from them can be used during the
build.

This is typically where you would list tools needed at build time but
not at run time, such as Autoconf, Automake, pkg-config, Gettext, or
Bison. guix lint can report likely mistakes in this area
(see Invoking guix lint).

self-native-input? (default: #f)

This is a Boolean field telling whether the package should use itself as
a native input when cross-compiling.

4.1.2 origin Reference

This section summarizes all the options available in origin
declarations (see Defining Packages).

Data Type: origin

This is the data type representing a source code origin.

uri

An object containing the URI of the source. The object type depends on
the method (see below). For example, when using the
url-fetch method of (guix download), the valid uri
values are: a URL represented as a string, or a list thereof.

method

A procedure that will handle the URI.

Examples include:

url-fetch from (guix download)

download a file the HTTP, HTTPS, or FTP URL specified in the
uri field;

git-fetch from (guix git-download)

clone the Git version control repository, and check out the revision
specified in the uri field as a git-reference object; a
git-reference looks like this:

A bytevector containing the SHA-256 hash of the source. Typically the
base32 form is used here to generate the bytevector from a
base-32 string.

file-name (default: #f)

The file name under which the source code should be saved. When this is
#f, a sensible default value will be used in most cases. In case
the source is fetched from a URL, the file name from the URL will be
used. For version control checkouts, it’s recommended to provide the
file name explicitly because the default is not very descriptive.

patches (default: '())

A list of file names containing patches to be applied to the source.

snippet (default: #f)

A quoted piece of code that will be run in the source directory to make
any modifications, which is sometimes more convenient than a patch.

patch-flags (default: '("-p1"))

A list of command-line flags that should be passed to the patch
command.

patch-inputs (default: #f)

Input packages or derivations to the patching process. When this is
#f, the usual set of inputs necessary for patching are provided,
such as GNU Patch.

modules (default: '())

A list of Guile modules that should be loaded during the patching
process and while running the code in the snippet field.

imported-modules (default: '())

The list of Guile modules to import in the patch derivation, for use by
the snippet.

patch-guile (default: #f)

The Guile package that should be used in the patching process. When
this is #f, a sensible default is used.

4.2 Build Systems

Each package definition specifies a build system and arguments for
that build system (see Defining Packages). This build-system
field represents the build procedure of the package, as well implicit
dependencies of that build procedure.

Build systems are <build-system> objects. The interface to
create and manipulate them is provided by the (guix build-system)
module, and actual build systems are exported by specific modules.

Under the hood, build systems first compile package objects to
bags. A bag is like a package, but with less
ornamentation—in other words, a bag is a lower-level representation of
a package, which includes all the inputs of that package, including some
that were implicitly added by the build system. This intermediate
representation is then compiled to a derivation (see Derivations).

Build systems accept an optional list of arguments. In package
definitions, these are passed via the arguments field
(see Defining Packages). They are typically keyword arguments
(see keyword arguments in Guile in GNU
Guile Reference Manual). The value of these arguments is usually
evaluated in the build stratum—i.e., by a Guile process launched
by the daemon (see Derivations).

The main build system is gnu-build-system, which implements the
standard build procedure for GNU packages and many other packages. It
is provided by the (guix build-system gnu) module.

In a nutshell, packages using it configured, built, and installed with
the usual ./configure && make && make check && make install
command sequence. In practice, a few additional steps are often needed.
All these steps are split up in separate phases,
notably5:

unpack

Unpack the source tarball, and change the current directory to the
extracted source tree. If the source is actually a directory, copy it
to the build tree, and enter that directory.

patch-source-shebangs

Patch shebangs encountered in source files so they refer to the right
store file names. For instance, this changes #!/bin/sh to
#!/gnu/store/…-bash-4.3/bin/sh.

configure

Run the configure script with a number of default options, such
as --prefix=/gnu/store/…, as well as the options specified
by the #:configure-flags argument.

build

Run make with the list of flags specified with
#:make-flags. If the #:parallel-builds? argument is true
(the default), build with make -j.

check

Run make check, or some other target specified with
#:test-target, unless #:tests? #f is passed. If the
#:parallel-tests? argument is true (the default), run make
check -j.

install

Run make install with the flags listed in #:make-flags.

patch-shebangs

Patch shebangs on the installed executable files.

strip

Strip debugging symbols from ELF files (unless #:strip-binaries?
is false), copying them to the debug output when available
(see Installing Debugging Files).

The build-side module (guix build gnu-build-system) defines
%standard-phases as the default list of build phases.
%standard-phases is a list of symbol/procedure pairs, where the
procedure implements the actual phase.

The list of phases used for a particular package can be changed with the
#:phases parameter. For instance, passing:

#:phases (alist-delete 'configure %standard-phases)

means that all the phases described above will be used, except the
configure phase.

In addition, this build system ensures that the “standard” environment
for GNU packages is available. This includes tools such as GCC, libc,
Coreutils, Bash, Make, Diffutils, grep, and sed (see the (guix
build-system gnu) module for a complete list.) We call these the
implicit inputs of a package, because package definitions don’t
have to mention them.

Other <build-system> objects are defined to support other
conventions and tools used by free software packages. They inherit most
of gnu-build-system, and differ mainly in the set of inputs
implicitly added to the build process, and in the list of phases
executed. Some of these build systems are listed below.

Scheme Variable: cmake-build-system

This variable is exported by (guix build-system cmake). It
implements the build procedure for packages using the
CMake build tool.

It automatically adds the cmake package to the set of inputs.
Which package is used can be specified with the #:cmake
parameter.

The #:configure-flags parameter is taken as a list of flags
passed to the cmake command. The #:build-type
parameter specifies in abstract terms the flags passed to the compiler;
it defaults to "RelWithDebInfo" (short for “release mode with
debugging information”), which roughly means that code is compiled with
-O2 -g, as is the case for Autoconf-based packages by default.

Scheme Variable: glib-or-gtk-build-system

This variable is exported by (guix build-system glib-or-gtk). It
is intended for use with packages making use of GLib or GTK+.

This build system adds the following two phases to the ones defined by
gnu-build-system:

glib-or-gtk-wrap

The phase glib-or-gtk-wrap ensures that programs found under
bin/ are able to find GLib’s “schemas” and
GTK+
modules. This is achieved by wrapping the programs in launch scripts
that appropriately set the XDG_DATA_DIRS and GTK_PATH
environment variables.

It is possible to exclude specific package outputs from that wrapping
process by listing their names in the
#:glib-or-gtk-wrap-excluded-outputs parameter. This is useful
when an output is known not to contain any GLib or GTK+ binaries, and
where wrapping would gratuitously add a dependency of that output on
GLib and GTK+.

glib-or-gtk-compile-schemas

The phase glib-or-gtk-compile-schemas makes sure that all GLib’s
GSettings schemas are compiled. Compilation is performed by the
glib-compile-schemas program. It is provided by the package
glib:bin which is automatically imported by the build system.
The glib package providing glib-compile-schemas can be
specified with the #:glib parameter.

Both phases are executed after the install phase.

Scheme Variable: python-build-system

This variable is exported by (guix build-system python). It
implements the more or less standard build procedure used by Python
packages, which consists in running python setup.py build and
then python setup.py install --prefix=/gnu/store/….

For packages that install stand-alone Python programs under bin/,
it takes care of wrapping these programs so their PYTHONPATH
environment variable points to all the Python libraries they depend on.

Which Python package is used can be specified with the #:python
parameter.

Scheme Variable: perl-build-system

This variable is exported by (guix build-system perl). It
implements the standard build procedure for Perl packages, which either
consists in running perl Build.PL --prefix=/gnu/store/…,
followed by Build and Build install; or in running
perl Makefile.PL PREFIX=/gnu/store/…, followed by
make and make install; depending on which of
Build.PL or Makefile.PL is present in the package
distribution. Preference is given to the former if both Build.PL
and Makefile.PL exist in the package distribution. This
preference can be reversed by specifying #t for the
#:make-maker? parameter.

This variable is exported by (guix build-system ruby). It
implements the RubyGems build procedure used by Ruby packages, which
involves running gem build followed by gem install.

Which Ruby package is used can be specified with the #:ruby
parameter. A list of additional flags to be passed to the gem
command can be specified with the #:gem-flags parameter.

Scheme Variable: waf-build-system

This variable is exported by (guix build-system waf). It
implements a build procedure around the waf script. The common
phases—configure, build, and install—are
implemented by passing their names as arguments to the waf
script.

The waf script is executed by the Python interpreter. Which
Python package is used to run the script can be specified with the
#:python parameter.

Scheme Variable: haskell-build-system

This variable is exported by (guix build-system haskell). It
implements the Cabal build procedure used by Haskell packages, which
involves running runhaskell Setup.hs configure
--prefix=/gnu/store/… and runhaskell Setup.hs build.
Instead of installing the package by running runhaskell Setup.hs
install, to avoid trying to register libraries in the read-only
compiler store directory, the build system uses runhaskell
Setup.hs copy, followed by runhaskell Setup.hs register. In
addition, the build system generates the package documentation by
running runhaskell Setup.hs haddock, unless #:haddock? #f
is passed. Optional Haddock parameters can be passed with the help of
the #:haddock-flags parameter. If the file Setup.hs is
not found, the build system looks for Setup.lhs instead.

Which Haskell compiler is used can be specified with the #:haskell
parameter which defaults to ghc.

Scheme Variable: emacs-build-system

This variable is exported by (guix build-system emacs). It
implements an installation procedure similar to the one of Emacs’ own
packaging system (see Packages in The GNU Emacs Manual).

It first creates the package-autoloads.el file, then it
byte compiles all Emacs Lisp files. Differently from the Emacs
packaging system, the Info documentation files are moved to the standard
documentation directory and the dir file is deleted. Each
package is installed in its own directory under
share/emacs/site-lisp/guix.d.

Lastly, for packages that do not need anything as sophisticated, a
“trivial” build system is provided. It is trivial in the sense that
it provides basically no support: it does not pull any implicit inputs,
and does not have a notion of build phases.

Scheme Variable: trivial-build-system

This variable is exported by (guix build-system trivial).

This build system requires a #:builder argument. This argument
must be a Scheme expression that builds the package’s output(s)—as
with build-expression->derivation (see build-expression->derivation).

4.3 The Store

Conceptually, the store is where derivations that have been
successfully built are stored—by default, under /gnu/store.
Sub-directories in the store are referred to as store paths. The
store has an associated database that contains information such has the
store paths referred to by each store path, and the list of valid
store paths—paths that result from a successful build.

The store is always accessed by the daemon on behalf of its clients
(see Invoking guix-daemon). To manipulate the store, clients
connect to the daemon over a Unix-domain socket, send it requests, and
read the result—these are remote procedure calls, or RPCs.

The (guix store) module provides procedures to connect to the
daemon, and to perform RPCs. These are described below.

Scheme Procedure: open-connection[file] [#:reserve-space? #t]

Connect to the daemon over the Unix-domain socket at file. When
reserve-space? is true, instruct it to reserve a little bit of
extra space on the file system so that the garbage collector can still
operate, should the disk become full. Return a server object.

file defaults to %default-socket-path, which is the normal
location given the options that were passed to configure.

Scheme Procedure: close-connectionserver

Close the connection to server.

Scheme Variable: current-build-output-port

This variable is bound to a SRFI-39 parameter, which refers to the port
where build and error logs sent by the daemon should be written.

Procedures that make RPCs all take a server object as their first
argument.

Scheme Procedure: valid-path?serverpath

Return #t when path is a valid store path.

Scheme Procedure: add-text-to-storeservernametext [references]

Add text under file name in the store, and return its store
path. references is the list of store paths referred to by the
resulting store path.

Scheme Procedure: build-derivationsserverderivations

Build derivations (a list of <derivation> objects or
derivation paths), and return when the worker is done building them.
Return #t on success.

Note that the (guix monads) module provides a monad as well as
monadic versions of the above procedures, with the goal of making it
more convenient to work with code that accesses the store (see The Store Monad).

4.4 Derivations

Low-level build actions and the environment in which they are performed
are represented by derivations. A derivation contain the
following pieces of information:

The outputs of the derivation—derivations produce at least one file or
directory in the store, but may produce more.

The inputs of the derivations, which may be other derivations or plain
files in the store (patches, build scripts, etc.)

The system type targeted by the derivation—e.g., x86_64-linux.

The file name of a build script in the store, along with the arguments
to be passed.

A list of environment variables to be defined.

Derivations allow clients of the daemon to communicate build actions to
the store. They exist in two forms: as an in-memory representation,
both on the client- and daemon-side, and as files in the store whose
name end in .drv—these files are referred to as derivation
paths. Derivations paths can be passed to the build-derivations
procedure to perform the build actions they prescribe (see The Store).

The (guix derivations) module provides a representation of
derivations as Scheme objects, along with procedures to create and
otherwise manipulate derivations. The lowest-level primitive to create
a derivation is the derivation procedure:

Build a derivation with the given arguments, and return the resulting
<derivation> object.

When hash and hash-algo are given, a
fixed-output derivation is created—i.e., one whose result is
known in advance, such as a file download. If, in addition,
recursive? is true, then that fixed output may be an executable
file or a directory and hash must be the hash of an archive
containing this output.

When references-graphs is true, it must be a list of file
name/store path pairs. In that case, the reference graph of each store
path is exported in the build environment in the corresponding file, in
a simple text format.

When allowed-references is true, it must be a list of store items
or outputs that the derivation’s output may refer to.

When leaked-env-vars is true, it must be a list of strings
denoting environment variables that are allowed to “leak” from the
daemon’s environment to the build environment. This is only applicable
to fixed-output derivations—i.e., when hash is true. The main
use is to allow variables such as http_proxy to be passed to
derivations that download files.

When local-build? is true, declare that the derivation is not a
good candidate for offloading and should rather be built locally
(see Daemon Offload Setup). This is the case for small derivations
where the costs of data transfers would outweigh the benefits.

When substitutable? is false, declare that substitutes of the
derivation’s output should not be used (see Substitutes). This is
useful, for instance, when building packages that capture details of the
host CPU instruction set.

Here’s an example with a shell script as its builder, assuming
store is an open connection to the daemon, and bash points
to a Bash executable in the store:

As can be guessed, this primitive is cumbersome to use directly. A
better approach is to write build scripts in Scheme, of course! The
best course of action for that is to write the build code as a
“G-expression”, and to pass it to gexp->derivation. For more
information, see G-Expressions.

Once upon a time, gexp->derivation did not exist and constructing
derivations with build code written in Scheme was achieved with
build-expression->derivation, documented below. This procedure
is now deprecated in favor of the much nicer gexp->derivation.

Return a derivation that executes Scheme expression exp as a
builder for derivation name. inputs must be a list of
(name drv-path sub-drv) tuples; when sub-drv is omitted,
"out" is assumed. modules is a list of names of Guile
modules from the current search path to be copied in the store,
compiled, and made available in the load path during the execution of
exp—e.g., ((guix build utils) (guix build
gnu-build-system)).

exp is evaluated in an environment where %outputs is bound
to a list of output/path pairs, and where %build-inputs is bound
to a list of string/output-path pairs made from inputs.
Optionally, env-vars is a list of string pairs specifying the name
and value of environment variables visible to the builder. The builder
terminates by passing the result of exp to exit; thus, when
exp returns #f, the build is considered to have failed.

exp is built using guile-for-build (a derivation). When
guile-for-build is omitted or is #f, the value of the
%guile-for-build fluid is used instead.

See the derivation procedure for the meaning of
references-graphs, allowed-references, local-build?,
and substitutable?.

Here’s an example of a single-output derivation that creates a directory
containing one file:

4.5 The Store Monad

The procedures that operate on the store described in the previous
sections all take an open connection to the build daemon as their first
argument. Although the underlying model is functional, they either have
side effects or depend on the current state of the store.

The former is inconvenient: the connection to the build daemon has to be
carried around in all those functions, making it impossible to compose
functions that do not take that parameter with functions that do. The
latter can be problematic: since store operations have side effects
and/or depend on external state, they have to be properly sequenced.

This is where the (guix monads) module comes in. This module
provides a framework for working with monads, and a particularly
useful monad for our uses, the store monad. Monads are a
construct that allows two things: associating “context” with values
(in our case, the context is the store), and building sequences of
computations (here computations include accesses to the store.) Values
in a monad—values that carry this additional context—are called
monadic values; procedures that return such values are called
monadic procedures.

There several things to note in the second version: the store
parameter is now implicit and is “threaded” in the calls to the
package->derivation and gexp->derivation monadic
procedures, and the monadic value returned by package->derivation
is bound using mlet instead of plain let.

As it turns out, the call to package->derivation can even be
omitted since it will take place implicitly, as we will see later
(see G-Expressions):

Calling the monadic sh-symlink has no effect. As someone once
said, “you exit a monad like you exit a building on fire: by running”.
So, to exit the monad and get the desired effect, one must use
run-with-store:

Note that the (guix monad-repl) module extends Guile’s REPL with
new “meta-commands” to make it easier to deal with monadic procedures:
run-in-store, and enter-store-monad. The former, is used
to “run” a single monadic value through the store:

Run mval, a monadic value in the store monad, in store, an
open store connection.

Monadic Procedure: text-filenametext [references]

Return as a monadic value the absolute file name in the store of the file
containing text, a string. references is a list of store items that the
resulting text file refers to; it defaults to the empty list.

Monadic Procedure: interned-filefile [name] [#:recursive? #t]

Return the name of file once interned in the store. Use
name as its store name, or the basename of file if
name is omitted.

When recursive? is true, the contents of file are added
recursively; if file designates a flat file and recursive?
is true, its contents are added, and its permission bits are kept.

The example below adds a file to the store, under two different names:

value in the absolute file name of file within the output
directory of package. When file is omitted, return the name
of the output directory of package. When target is
true, use it as a cross-compilation target triplet.

Monadic Procedure: package->derivationpackage [system]

Monadic Procedure: package->cross-derivationpackagetarget [system]

Monadic version of package-derivation and
package-cross-derivation (see Defining Packages).

4.6 G-Expressions

So we have “derivations”, which represent a sequence of build actions
to be performed to produce an item in the store (see Derivations).
Those build actions are performed when asking the daemon to actually
build the derivations; they are run by the daemon in a container
(see Invoking guix-daemon).

It should come as no surprise that we like to write those build actions
in Scheme. When we do that, we end up with two strata of Scheme
code7: the “host code”—code that defines packages, talks
to the daemon, etc.—and the “build code”—code that actually
performs build actions, such as making directories, invoking
make, etc.

To describe a derivation and its build actions, one typically needs to
embed build code inside host code. It boils down to manipulating build
code as data, and Scheme’s homoiconicity—code has a direct
representation as data—comes in handy for that. But we need more than
Scheme’s normal quasiquote mechanism to construct build
expressions.

The (guix gexp) module implements G-expressions, a form of
S-expressions adapted to build expressions. G-expressions, or
gexps, consist essentially in three syntactic forms: gexp,
ungexp, and ungexp-splicing (or simply: #~,
#$, and #$@), which are comparable respectively to
quasiquote, unquote, and unquote-splicing
(see quasiquote in GNU Guile
Reference Manual). However, there are major differences:

Gexps are meant to be written to a file and run or manipulated by other
processes.

When a high-level object such as a package or derivation is unquoted
inside a gexp, the result is as if its output file name had been
introduced.

Gexps carry information about the packages or derivations they refer to,
and these dependencies are automatically added as inputs to the build
processes that use them.

This mechanism is not limited to package and derivation
objects: compilers able to “lower” other high-level objects to
derivations can be defined, such that these objects can also be inserted
into gexps. For example, a useful type of high-level object that can be
inserted in a gexp is “file-like objects”, which make it easy to
add files to the store and refer to them in
derivations and such (see local-file and plain-file
below.)

This gexp can be passed to gexp->derivation; we obtain a
derivation that builds a directory containing exactly one symlink to
/gnu/store/…-coreutils-8.22/bin/ls:

(gexp->derivation "the-thing" build-exp)

As one would expect, the "/gnu/store/…-coreutils-8.22" string is
substituted to the reference to the coreutils package in the
actual build code, and coreutils is automatically made an input to
the derivation. Likewise, #$output (equivalent to (ungexp
output)) is replaced by a string containing the derivation’s output
directory name.

In a cross-compilation context, it is useful to distinguish between
references to the native build of a package—that can run on the
host—versus references to cross builds of a package. To that end, the
#+ plays the same role as #$, but is a reference to a
native package build:

In the example above, the native build of coreutils is used, so
that ln can actually run on the host; but then the
cross-compiled build of emacs is referenced.

The syntactic form to construct gexps is summarized below.

Scheme Syntax: #~exp

Scheme Syntax: (gexpexp)

Return a G-expression containing exp. exp may contain one
or more of the following forms:

#$obj

(ungexp obj)

Introduce a reference to obj. obj may have one of the
supported types, for example a package or a
derivation, in which case the ungexp form is replaced by its
output file name—e.g., "/gnu/store/…-coreutils-8.22.

If obj is a list, it is traversed and references to supported
objects are substituted similarly.

If obj is another gexp, its contents are inserted and its
dependencies are added to those of the containing gexp.

If obj is another kind of object, it is inserted as is.

#$obj:output

(ungexp objoutput)

This is like the form above, but referring explicitly to the
output of obj—this is useful when obj produces
multiple outputs (see Packages with Multiple Outputs).

#+obj

#+obj:output

(ungexp-native obj)

(ungexp-native objoutput)

Same as ungexp, but produces a reference to the native
build of obj when used in a cross compilation context.

#$output[:output]

(ungexp output [output])

Insert a reference to derivation output output, or to the main
output when output is omitted.

This only makes sense for gexps passed to gexp->derivation.

#$@lst

(ungexp-splicing lst)

Like the above, but splices the contents of lst inside the
containing list.

#+@lst

(ungexp-native-splicing lst)

Like the above, but refers to native builds of the objects listed in
lst.

G-expressions created by gexp or #~ are run-time objects
of the gexp? type (see below.)

Scheme Procedure: gexp?obj

Return #t if obj is a G-expression.

G-expressions are meant to be written to disk, either as code building
some derivation, or as plain files in the store. The monadic procedures
below allow you to do that (see The Store Monad, for more
information about monads.)

Return a derivation name that runs exp (a gexp) with
guile-for-build (a derivation) on system. When target
is true, it is used as the cross-compilation target triplet for packages
referred to by exp.

Make modules available in the evaluation context of exp;
modules is a list of names of Guile modules searched in
module-path to be copied in the store, compiled, and made available in
the load path during the execution of exp—e.g., ((guix
build utils) (guix build gnu-build-system)).

graft? determines whether packages referred to by exp should be grafted when
applicable.

When references-graphs is true, it must be a list of tuples of one of the
following forms:

The right-hand-side of each element of references-graphs is automatically made
an input of the build process of exp. In the build environment, each
file-name contains the reference graph of the corresponding item, in a simple
text format.

allowed-references must be either #f or a list of output names and packages.
In the latter case, the list denotes store items that the result is allowed to
refer to. Any reference to another store item will lead to a build error.

The effect here is to “intern” /tmp/my-nscd.conf by copying it
to the store. Once expanded, for instance viagexp->derivation, the G-expression refers to that copy under
/gnu/store; thus, modifying or removing the file in /tmp
does not have any effect on what the G-expression does.
plain-file can be used similarly; it differs in that the file
content is directly passed as a string.

Scheme Procedure: local-filefile [name] [#:recursive? #t]

Return an object representing local file file to add to the store; this
object can be used in a gexp. file will be added to the store under name–by
default the base name of file.

When recursive? is true, the contents of file are added recursively; if file
designates a flat file and recursive? is true, its contents are added, and its
permission bits are kept.

This is the declarative counterpart of the interned-file monadic
procedure (see interned-file).

Scheme Procedure: plain-filenamecontent

Return an object representing a text file called name with the given
content (a string) to be added to the store.

This is the declarative counterpart of text-file.

Monadic Procedure: gexp->scriptnameexp

Return an executable script name that runs exp using
guile with modules in its search path.

The resulting file holds references to all the dependencies of exp
or a subset thereof.

Monadic Procedure: text-file*nametext …

Return as a monadic value a derivation that builds a text file
containing all of text. text may list, in addition to
strings, objects of any type that can be used in a gexp: packages,
derivations, local file objects, etc. The resulting store file holds
references to all these.

This variant should be preferred over text-file anytime the file
to create will reference items from the store. This is typically the
case when building a configuration file that embeds store file names,
like this:

In this example, the resulting /gnu/store/…-profile.sh file
will references coreutils, grep, and sed, thereby
preventing them from being garbage-collected during its lifetime.

Of course, in addition to gexps embedded in “host” code, there are
also modules containing build tools. To make it clear that they are
meant to be used in the build stratum, these modules are kept in the
(guix build …) name space.

5.1 Invoking guix build

The guix build command builds packages or derivations and
their dependencies, and prints the resulting store paths. Note that it
does not modify the user’s profile—this is the job of the
guix package command (see Invoking guix package). Thus,
it is mainly useful for distribution developers.

The general syntax is:

guix build optionspackage-or-derivation…

package-or-derivation may be either the name of a package found in
the software distribution such as coreutils or
coreutils-8.20, or a derivation such as
/gnu/store/…-coreutils-8.19.drv. In the former case, a
package with the corresponding name (and optionally version) is searched
for among the GNU distribution modules (see Package Modules).

Alternatively, the --expression option may be used to specify a
Scheme expression that evaluates to a package; this is useful when
disambiguation among several same-named packages or package variants is
needed.

The options may be zero or more of the following:

--expression=expr

-e expr

Build the package or derivation expr evaluates to.

For example, expr may be (@ (gnu packages guile)
guile-1.8), which unambiguously designates this specific variant of
version 1.8 of Guile.

Alternately, expr may be a G-expression, in which case it is used
as a build program passed to gexp->derivation
(see G-Expressions).

Lastly, expr may refer to a zero-argument monadic procedure
(see The Store Monad). The procedure must return a derivation as a
monadic value, which is then passed through run-with-store.

--source

-S

Build the packages’ source derivations, rather than the packages
themselves.

The returned source tarball is the result of applying any patches and
code snippets specified in the package’s origin (see Defining Packages).

--sources

Fetch and return the source of package-or-derivation and all their
dependencies, recursively. This is a handy way to obtain a local copy
of all the source code needed to build packages, allowing you to
eventually build them even without network access. It is an extension
of the --source option and can accept one of the following
optional argument values:

package

This value causes the --sources option to behave in the same way
as the --source option.

all

Build all packages’ source derivations, including any source that might
be listed as inputs. This is the default value.

$ guix build --sources tzdata
The following derivations will be built:
/gnu/store/…-tzdata2015b.tar.gz.drv
/gnu/store/…-tzcode2015b.tar.gz.drv

transitive

Build all packages’ source derivations, as well as all source
derivations for packages’ transitive inputs. This can be used e.g. to
prefetch package source for later offline building.

Attempt to build for system—e.g., i686-linux—instead of
the host’s system type.

An example use of this is on Linux-based systems, which can emulate
different personalities. For instance, passing
--system=i686-linux on an x86_64-linux system allows users
to build packages in a complete 32-bit environment.

--target=triplet

Cross-build for triplet, which must be a valid GNU triplet, such
as "mips64el-linux-gnu" (see GNU
configuration triplets in GNU Configure and Build System).

--with-source=source

Use source as the source of the corresponding package.
source must be a file name or a URL, as for guix
download (see Invoking guix download).

The “corresponding package” is taken to be one specified on the
command line whose name matches the base of source—e.g., if
source is /src/guile-2.0.10.tar.gz, the corresponding
package is guile. Likewise, the version string is inferred from
source; in the previous example, it’s 2.0.10.

This option allows users to try out versions of packages other than the
one provided by the distribution. The example below downloads
ed-1.7.tar.gz from a GNU mirror and uses that as the source for
the ed package:

guix build ed --with-source=mirror://gnu/ed/ed-1.7.tar.gz

As a developer, --with-source makes it easy to test release
candidates:

This allows users to define their own packages and make them visible to
the command-line tools.

--keep-failed

-K

Keep the build tree of failed builds. Thus, if a build fail, its build
tree is kept under /tmp, in a directory whose name is shown at
the end of the build log. This is useful when debugging build issues.

--dry-run

-n

Do not build the derivations.

--fallback

When substituting a pre-built binary fails, fall back to building
packages locally.

When the build or substitution process remains silent for more than
seconds, terminate it and report a build failure.

--timeout=seconds

Likewise, when the build or substitution process lasts for more than
seconds, terminate it and report a build failure.

By default there is no timeout. This behavior can be restored with
--timeout=0.

--verbosity=level

Use the given verbosity level. level must be an integer between 0
and 5; higher means more verbose output. Setting a level of 4 or more
may be helpful when debugging setup issues with the build daemon.

--cores=n

-c n

Allow the use of up to n CPU cores for the build. The special
value 0 means to use as many CPU cores as available.

--max-jobs=n

-M n

Allow at most n build jobs in parallel. See --max-jobs, for details about this option and the
equivalent guix-daemon option.

Behind the scenes, guix build is essentially an interface to
the package-derivation procedure of the (guix packages)
module, and to the build-derivations procedure of the (guix
derivations) module.

In addition to options explicitly passed on the command line,
guix build and other guix commands that support
building honor the GUIX_BUILD_OPTIONS environment variable.

Environment Variable: GUIX_BUILD_OPTIONS

Users can define this variable to a list of command line options that
will automatically be used by guix build and other
guix commands that can perform builds, as in the example
below:

$ export GUIX_BUILD_OPTIONS="--no-substitutes -c 2 -L /foo/bar"

These options are parsed independently, and the result is appended to
the parsed command-line options.

5.2 Invoking guix edit

So many packages, so many source files! The guix edit command
facilitates the life of packagers by pointing their editor at the source
file containing the definition of the specified packages. For instance:

guix edit gcc-4.8 vim

launches the program specified in the EDITOR environment variable
to edit the recipe of GCC 4.8.4 and that of Vim.

If you are using Emacs, note that the Emacs user interface provides
similar functionality in the “package info” and “package list”
buffers created by M-x guix-search-by-name and similar commands
(see Emacs Commands).

5.3 Invoking guix download

When writing a package definition, developers typically need to download
the package’s source tarball, compute its SHA256 hash, and write that
hash in the package definition (see Defining Packages). The
guix download tool helps with this task: it downloads a file
from the given URI, adds it to the store, and prints both its file name
in the store and its SHA256 hash.

The fact that the downloaded file is added to the store saves bandwidth:
when the developer eventually tries to build the newly defined package
with guix build, the source tarball will not have to be
downloaded again because it is already in the store. It is also a
convenient way to temporarily stash files, which may be deleted
eventually (see Invoking guix gc).

The guix download command supports the same URIs as used in
package definitions. In particular, it supports mirror:// URIs.
https URIs (HTTP over TLS) are supported provided the
Guile bindings for GnuTLS are available in the user’s environment; when
they are not available, an error is raised. See how to install the GnuTLS bindings for Guile in GnuTLS-Guile, for more information.

The following option is available:

--format=fmt

-f fmt

Write the hash in the format specified by fmt. For more
information on the valid values for fmt, see Invoking guix hash.

5.4 Invoking guix hash

The guix hash command computes the SHA256 hash of a file.
It is primarily a convenience tool for anyone contributing to the
distribution: it computes the cryptographic hash of a file, which can be
used in the definition of a package (see Defining Packages).

The general syntax is:

guix hash optionfile

guix hash has the following option:

--format=fmt

-f fmt

Write the hash in the format specified by fmt.

Supported formats: nix-base32, base32, base16
(hex and hexadecimal can be used as well).

If the --format option is not specified, guix hash
will output the hash in nix-base32. This representation is used
in the definitions of packages.

--recursive

-r

Compute the hash on file recursively.

In this case, the hash is computed on an archive containing file,
including its children if it is a directory. Some of file’s
meta-data is part of the archive; for instance, when file is a
regular file, the hash is different depending on whether file is
executable or not. Meta-data such as time stamps has no impact on the
hash (see Invoking guix archive).

5.5 Invoking guix import

The guix import command is useful for people willing to add a
package to the distribution but who’d rather do as little work as
possible to get there—a legitimate demand. The command knows of a few
repositories from which it can “import” package meta-data. The result
is a package definition, or a template thereof, in the format we know
(see Defining Packages).

The general syntax is:

guix import importeroptions…

importer specifies the source from which to import package
meta-data, and options specifies a package identifier and other
options specific to importer. Currently, the available
“importers” are:

gnu

Import meta-data for the given GNU package. This provides a template
for the latest version of that GNU package, including the hash of its
source tarball, and its canonical synopsis and description.

Additional information such as the package’s dependencies and its
license needs to be figured out manually.

For example, the following command returns a package definition for
GNU Hello:

guix import gnu hello

Specific command-line options are:

--key-download=policy

As for guix refresh, specify the policy to handle missing OpenPGP
keys when verifying the package’s signature. See --key-download.

pypi

Import meta-data from the Python Package
Index8. Information is taken from the JSON-formatted
description available at pypi.python.org and usually includes all
the relevant information, including package dependencies.

The command below imports meta-data for the itsdangerous Python
package:

guix import pypi itsdangerous

cpan

Import meta-data from MetaCPAN.
Information is taken from the JSON-formatted meta-data provided through
MetaCPAN’s API and includes most
relevant information, such as module dependencies. License information
should be checked closely. If Perl is available in the store, then the
corelist utility will be used to filter core modules out of the
list of dependencies.

Import meta-data from a local copy of the source of the
Nixpkgs distribution9. Package definitions in Nixpkgs are
typically written in a mixture of Nix-language and Bash code. This
command only imports the high-level package structure that is written in
the Nix language. It normally includes all the basic fields of a
package definition.

When importing a GNU package, the synopsis and descriptions are replaced
by their canonical upstream variant.

As an example, the command below imports the package definition of
LibreOffice (more precisely, it imports the definition of the package
bound to the libreoffice top-level attribute):

guix import nix ~/path/to/nixpkgs libreoffice

hackage

Import meta-data from Haskell community’s central package archive
Hackage. Information is taken from
Cabal files and includes all the relevant information, including package
dependencies.

Specific command-line options are:

--stdin

-s

Read a Cabal file from the standard input.

--no-test-dependencies

-t

Do not include dependencies required by the test suites only.

--cabal-environment=alist

-e alist

alist is a Scheme alist defining the environment in which the
Cabal conditionals are evaluated. The accepted keys are: os,
arch, impl and a string representing the name of a flag.
The value associated with a flag has to be either the symbol
true or false. The value associated with other keys
has to conform to the Cabal file format definition. The default value
associated with the keys os, arch and impl is
‘linux’, ‘x86_64’ and ‘ghc’ respectively.

The command below imports meta-data for the latest version of the
HTTP Haskell package without including test dependencies and
specifying the value of the flag ‘network-uri’ as false:

guix import hackage -t -e "'((\"network-uri\" . false))" HTTP

A specific package version may optionally be specified by following the
package name by a hyphen and a version number as in the following example:

5.6 Invoking guix refresh

The primary audience of the guix refresh command is developers
of the GNU software distribution. By default, it reports any packages
provided by the distribution that are outdated compared to the latest
upstream version, like this:

$ guix refresh
gnu/packages/gettext.scm:29:13: gettext would be upgraded from 0.18.1.1 to 0.18.2.1
gnu/packages/glib.scm:77:12: glib would be upgraded from 2.34.3 to 2.37.0

It does so by browsing each package’s FTP directory and determining the
highest version number of the source tarballs
therein10.

When passed --update, it modifies distribution source files to
update the version numbers and source tarball hashes of those packages’
recipes (see Defining Packages). This is achieved by downloading
each package’s latest source tarball and its associated OpenPGP
signature, authenticating the downloaded tarball against its signature
using gpg, and finally computing its hash. When the public
key used to sign the tarball is missing from the user’s keyring, an
attempt is made to automatically retrieve it from a public key server;
when it’s successful, the key is added to the user’s keyring; otherwise,
guix refresh reports an error.

The core subset refers to all the packages at the core of the
distribution—i.e., packages that are used to build “everything
else”. This includes GCC, libc, Binutils, Bash, etc. Usually,
changing one of these packages in the distribution entails a rebuild of
all the others. Thus, such updates are an inconvenience to users in
terms of build time or bandwidth used to achieve the upgrade.

The non-core subset refers to the remaining packages. It is
typically useful in cases where an update of the core packages would be
inconvenient.

In addition, guix refresh can be passed one or more package
names, as in this example:

guix refresh -u emacs idutils gcc-4.8.4

The command above specifically updates the emacs and
idutils packages. The --select option would have no
effect in this case.

When considering whether to upgrade a package, it is sometimes
convenient to know which packages would be affected by the upgrade and
should be checked for compatibility. For this the following option may
be used when passing guix refresh one or more package names:

--list-dependent

-l

List top-level dependent packages that would need to be rebuilt as a
result of upgrading one or more packages.

Be aware that the --list-dependent option only
approximates the rebuilds that would be required as a result of
an upgrade. More rebuilds might be required under some circumstances.

5.7 Invoking guix lint

The guix lint is meant to help package developers avoid common
errors and use a consistent style. It runs a number of checks on a
given set of packages in order to find common mistakes in their
definitions. Available checkers include (see
--list-checkers for a complete list):

5.8 Invoking guix size

The guix size command helps package developers profile the
disk usage of packages. It is easy to overlook the impact of an
additional dependency added to a package, or the impact of using a
single output for a package that could easily be split (see Packages with Multiple Outputs). These are the typical issues that
guix size can highlight.

The command can be passed a package specification such as gcc-4.8
or guile:debug, or a file name in the store. Consider this
example:

The store items listed here constitute the transitive closure of
Coreutils—i.e., Coreutils and all its dependencies, recursively—as
would be returned by:

$ guix gc -R /gnu/store/…-coreutils-8.23

Here the output shows 3 columns next to store items. The first column,
labeled “total”, shows the size in mebibytes (MiB) of the closure of
the store item—that is, its own size plus the size of all its
dependencies. The next column, labeled “self”, shows the size of the
item itself. The last column shows the ratio of the item’s size to the
space occupied by all the items listed here.

In this example, we see that the closure of Coreutils weighs in at
70 MiB, half of which is taken by libc. (That libc represents a
large fraction of the closure is not a problem per se because it is
always available on the system anyway.)

When the package passed to guix size is available in the
store, guix size queries the daemon to determine its
dependencies, and measures its size in the store, similar to du
-ms --apparent-size (see du invocation in GNU
Coreutils).

When the given package is not in the store, guix size
reports information based on information about the available substitutes
(see Substitutes). This allows it to profile disk usage of store
items that are not even on disk, only available remotely.

The available options are:

--map-file=file

Write to file a graphical map of disk usage as a PNG file.

For the example above, the map looks like this:

This option requires that
Guile-Charting be
installed and visible in Guile’s module search path. When that is not
the case, guix size fails as it tries to load it.

5.9 Invoking guix environment

The purpose of guix environment is to assist hackers in
creating reproducible development environments without polluting their
package profile. The guix environment tool takes one or more
packages, builds all of the necessary inputs, and creates a shell
environment to use them.

The general syntax is:

guix environment optionspackage…

The following example spawns a new shell set up for the development of
GNU Guile:

guix environment guile

If the specified packages are not built yet, guix environment
automatically builds them. The new shell’s environment is an augmented
version of the environment that guix environment was run in.
It contains the necessary search paths for building the given package
added to the existing environment variables. To create a “pure”
environment in which the original environment variables have been unset,
use the --pure option11.

guix environment defines the GUIX_ENVIRONMENT
variable in the shell it spaws. This allows users to, say, define a
specific prompt for development environments in their .bashrc
(see Bash Startup Files in The GNU Bash Reference Manual):

if [ -n "$GUIX_ENVIRONMENT" ]
then
export PS1="\u@\h \w [dev]\$ "
fi

Additionally, more than one package may be specified, in which case the
union of the inputs for the given packages are used. For example, the
command below spawns a shell where all of the dependencies of both Guile
and Emacs are available:

guix environment guile emacs

Sometimes an interactive shell session is not desired. The
--exec option can be used to specify the command to run instead.

guix environment guile --exec=make

In other situations, it is more convenient to specify the list of
packages needed in the environment. For example, the following command
runs python from an environment containing Python 2.7 and
NumPy:

guix environment --ad-hoc python2-numpy python-2.7 -E python

The available options are summarized below.

--expression=expr

-e expr

Create an environment for the package that expr evaluates to.

For example, running:

guix environment -e '(@ (gnu packages maths) petsc-openmpi)'

starts a shell with the environment for this specific variant of the
PETSc package.

--load=file

-l file

Create an environment for the package that the code within file
evaluates to.

Include all specified packages in the resulting environment, as if an
ad hoc package were defined with them as inputs. This option is
useful for quickly creating an environment without having to write a
package expression to contain the desired inputs.

For instance, the command:

guix environment --ad-hoc guile guile-sdl -E guile

runs guile in an environment where Guile and Guile-SDL are
available.

Note that this example implicitly asks for the default output of
guile and guile-sdl but it is possible to ask for a
specific output—e.g., glib:bin asks for the bin output
of glib (see Packages with Multiple Outputs).

--pure

Unset existing environment variables when building the new environment.
This has the effect of creating an environment in which search paths
only contain package inputs.

--search-paths

Display the environment variable definitions that make up the
environment.

--system=system

-s system

Attempt to build for system—e.g., i686-linux.

It also supports all of the common build options that guix
build supports (see common build options).

5.10 Invoking guix publish

The purpose of guix publish is to enable users to easily share
their store with others, which can then use it as a substitute server
(see Substitutes).

When guix publish runs, it spawns an HTTP server which allows
anyone with network access to obtain substitutes from it. This means
that any machine running Guix can also act as if it were a build farm,
since the HTTP interface is compatible with Hydra, the software behind
the hydra.gnu.org build farm.

For security, each substitute is signed, allowing recipients to check
their authenticity and integrity (see Substitutes). Because
guix publish uses the system’s signing key, which is only
readable by the system administrator, it must be started as root; the
--user option makes it drop root privileges early on.

The general syntax is:

guix publish options…

Running guix publish without any additional arguments will
spawn an HTTP server on port 8080:

guix publish

Once a publishing server has been authorized (see Invoking guix archive), the daemon may download substitutes from it:

guix-daemon --substitute-urls=http://example.org:8080

The following options are available:

--port=port

-p port

Listen for HTTP requests on port.

--listen=host

Listen on the network interface for host. The default is to
accept connections from any interface.

--user=user

-u user

Change privileges to user as soon as possible—i.e., once the
server socket is open and the signing key has been read.

--repl[=port]

-r [port]

Spawn a Guile REPL server (see REPL Servers in GNU Guile
Reference Manual) on port (37146 by default). This is used
primarily for debugging a running guix publish server.

6 GNU Distribution

Guix comes with a distribution of the GNU system consisting entirely of
free software12. The
distribution can be installed on its own (see System Installation),
but it is also possible to install Guix as a package manager on top of
an installed GNU/Linux system (see Installation). To distinguish
between the two, we refer to the standalone distribution as the Guix
System Distribution, or GuixSD.

The distribution provides core GNU packages such as GNU libc, GCC, and
Binutils, as well as many GNU and non-GNU applications. The complete
list of available packages can be browsed
on-line or by
running guix package (see Invoking guix package):

guix package --list-available

Our goal has been to provide a practical 100% free software distribution of
Linux-based and other variants of GNU, with a focus on the promotion and
tight integration of GNU components, and an emphasis on programs and
tools that help users exert that freedom.

Packages are currently available on the following platforms:

x86_64-linux

Intel/AMD x86_64 architecture, Linux-Libre kernel;

i686-linux

Intel 32-bit architecture (IA32), Linux-Libre kernel;

armhf-linux

ARMv7-A architecture with hard float, Thumb-2 and NEON,
using the EABI hard-float ABI, and Linux-Libre kernel.

6.1 System Installation

This section explains how to install the Guix System Distribution
on a machine. The Guix package manager can
also be installed on top of a running GNU/Linux system,
see Installation.

6.1.1 Limitations

As of version 0.8.3, the Guix System Distribution (GuixSD) is
not production-ready. It may contain bugs and lack important
features. Thus, if you are looking for a stable production system that
respects your freedom as a computer user, a good solution at this point
is to consider one of
more established GNU/Linux distributions. We hope you can soon switch
to the GuixSD without fear, of course. In the meantime, you can
also keep using your distribution and try out the package manager on top
of it (see Installation).

Before you proceed with the installation, be aware of the following
noteworthy limitations applicable to version 0.8.3:

The installation process does not include a graphical user interface and
requires familiarity with GNU/Linux (see the following subsections to
get a feel of what that means.)

The system does not yet provide full GNOME and KDE desktops. Xfce and
Enlightenment are available though, if graphical desktop environments
are your thing, as well as a number of X11 window managers.

Support for the Logical Volume Manager (LVM) is missing.

Few system services are currently supported out-of-the-box
(see Services).

More than 2,000 packages are available, but you may
occasionally find that a useful package is missing.

You’ve been warned. But more than a disclaimer, this is an invitation
to report issues (and success stories!), and join us in improving it.
See Contributing, for more info.

6.1.2 USB Stick Installation

An installation image for USB sticks can be downloaded from
‘ftp://alpha.gnu.org/gnu/guix/guixsd-usb-install-0.8.3.system.xz’,
where system is one of:

x86_64-linux

for a GNU/Linux system on Intel/AMD-compatible 64-bit CPUs;

i686-linux

for a 32-bit GNU/Linux system on Intel-compatible CPUs.

This image contains a single partition with the tools necessary for an
installation. It is meant to be copied as is to a large-enough
USB stick.

To copy the image to a USB stick, follow these steps:

Decompress the image using the xz command:

xz -d guixsd-usb-install-0.8.3.system.xz

Insert a USB stick of 1 GiB or more in your machine, and determine
its device name. Assuming that USB stick is known as /dev/sdX,
copy the image with:

dd if=guixsd-usb-install-0.8.3.x86_64 of=/dev/sdX

Access to /dev/sdX usually requires root privileges.

Once this is done, you should be able to reboot the system and boot from
the USB stick. The latter usually requires you to get in the BIOS’ boot
menu, where you can choose to boot from the USB stick.

6.1.3 Preparing for Installation

Once you have successfully booted the image on the USB stick, you should
end up with a root prompt. Several console TTYs are configured and can
be used to run commands as root. TTY2 shows this documentation,
browsable using the Info reader commands (see Help in Info: An
Introduction).

To install the system, you would:

Configure the network, by running ifconfig eno1 up && dhclient
eno1 (to get an automatically assigned IP address from the wired
network interface controller13),
or using the ifconfig command.

The system automatically loads drivers for your network interface
controllers.

Setting up network access is almost always a requirement because the
image does not contain all the software and tools that may be needed.

Unless this has already been done, you must partition and format the
target partitions.

Preferably, assign partitions a label so that you can easily and
reliably refer to them in file-system declarations (see File Systems). This is typically done using the -L option of
mkfs.ext4 and related commands.

This will make /gnu/store copy-on-write, such that packages added
to it during the installation phase will be written to the target disk
rather than kept in memory.

6.1.4 Proceeding with the Installation

With the target partitions ready, you now have to edit a file and
provide the declaration of the operating system to be installed. To
that end, the installation system comes with two text editors: GNU nano
(see GNU nano Manual), and GNU Zile, an Emacs clone.
It is better to store that file on the target root file system, say, as
/mnt/etc/config.scm.

See Using the Configuration System, for examples of operating system
configurations. These examples are available under
/etc/configuration in the installation image, so you can copy
them and use them as a starting point for your own configuration.

Once you are done preparing the configuration file, the new system must
be initialized (remember that the target root file system is mounted
under /mnt):

guix system init /mnt/etc/config.scm /mnt

This will copy all the necessary files, and install GRUB on
/dev/sdX, unless you pass the --no-grub option. For
more information, see Invoking guix system. This command may trigger
downloads or builds of missing packages, which can take some time.

Once that command has completed—and hopefully succeeded!—you can
run reboot and boot into the new system. Cross fingers, and
join us on #guix on the Freenode IRC network or on
guix-devel@gnu.org to share your experience—good or not so
good.

6.1.5 Building the Installation Image

The installation image described above was built using the guix
system command, specifically:

guix system disk-image --image-size=850MiB gnu/system/install.scm

See Invoking guix system, for more information. See
gnu/system/install.scm in the source tree for more information
about the installation image.

6.2 System Configuration

The Guix System Distribution supports a consistent whole-system configuration
mechanism. By that we mean that all aspects of the global system
configuration—such as the available system services, timezone and
locale settings, user accounts—are declared in a single place. Such
a system configuration can be instantiated—i.e., effected.

One of the advantages of putting all the system configuration under the
control of Guix is that it supports transactional system upgrades, and
makes it possible to roll-back to a previous system instantiation,
should something go wrong with the new one (see Features). Another
one is that it makes it easy to replicate the exact same configuration
across different machines, or at different points in time, without
having to resort to additional administration tools layered on top of
the system’s own tools.

This section describes this mechanism. First we focus on the system
administrator’s viewpoint—explaining how the system is configured and
instantiated. Then we show how this mechanism can be extended, for
instance to support new system services.

6.2.1 Using the Configuration System

The operating system is configured by providing an
operating-system declaration in a file that can then be passed to
the guix system command (see Invoking guix system). A
simple setup, with the default system services, the default Linux-Libre
kernel, initial RAM disk, and boot loader looks like this:

This example should be self-describing. Some of the fields defined
above, such as host-name and bootloader, are mandatory.
Others, such as packages and services, can be omitted, in
which case they get a default value.

The packages field lists
packages that will be globally visible on the system, for all user
accounts—i.e., in every user’s PATH environment variable—in
addition to the per-user profiles (see Invoking guix package). The
%base-packages variable provides all the tools one would expect
for basic user and administrator tasks—including the GNU Core
Utilities, the GNU Networking Utilities, the GNU Zile lightweight text
editor, find, grep, etc. The example above adds
Emacs to those, taken from the (gnu packages emacs) module
(see Package Modules).

The services field lists system services to be made
available when the system starts (see Services).
The operating-system declaration above specifies that, in
addition to the basic services, we want the lshd secure shell
daemon listening on port 2222, and allowing remote root logins
(see Invoking lshd in GNU lsh Manual). Under the hood,
lsh-service arranges so that lshd is started with the
right command-line options, possibly with supporting configuration files
generated as needed (see Defining Services). See operating-system Reference, for details about the available operating-system
fields.

The configuration for a typical “desktop” usage, with the X11 display
server, a desktop environment, network management, an SSH server, and
more, would look like this:

See Desktop Services, for the exact list of services provided by
%desktop-services. See X.509 Certificates, for background
information about the nss-certs package that is used here.

Assuming the above snippet is stored in the my-system-config.scm
file, the guix system reconfigure my-system-config.scm command
instantiates that configuration, and makes it the default GRUB boot
entry (see Invoking guix system). The normal way to change the
system’s configuration is by updating this file and re-running the
guix system command.

At the Scheme level, the bulk of an operating-system declaration
is instantiated with the following monadic procedure (see The Store Monad):

6.2.3 File Systems

The list of file systems to be mounted is specified in the
file-systems field of the operating system’s declaration
(see Using the Configuration System). Each file system is declared
using the file-system form, like this:

As usual, some of the fields are mandatory—those shown in the example
above—while others can be omitted. These are described below.

Data Type: file-system

Objects of this type represent file systems to be mounted. They
contain the following members:

type

This is a string specifying the type of the file system—e.g.,
"ext4".

mount-point

This designates the place where the file system is to be mounted.

device

This names the “source” of the file system. By default it is the name
of a node under /dev, but its meaning depends on the title
field described below.

title (default: 'device)

This is a symbol that specifies how the device field is to be
interpreted.

When it is the symbol device, then the device field is
interpreted as a file name; when it is label, then device
is interpreted as a partition label name; when it is uuid,
device is interpreted as a partition unique identifier (UUID).

UUIDs may be converted from their string representation (as shown by the
tune2fs -l command) using the uuid form, like this:

The label and uuid options offer a way to refer to disk
partitions without having to hard-code their actual device
name15.

However, when a file system’s source is a mapped device (see Mapped Devices), its device field must refer to the mapped
device name—e.g., /dev/mapper/root-partition—and consequently
title must be set to 'device. This is required so that
the system knows that mounting the file system depends on having the
corresponding device mapping established.

flags (default: '())

This is a list of symbols denoting mount flags. Recognized flags
include read-only, bind-mount, no-dev (disallow
access to special files), no-suid (ignore setuid and setgid
bits), and no-exec (disallow program execution.)

options (default: #f)

This is either #f, or a string denoting mount options.

needed-for-boot? (default: #f)

This Boolean value indicates whether the file system is needed when
booting. If that is true, then the file system is mounted when the
initial RAM disk (initrd) is loaded. This is always the case, for
instance, for the root file system.

check? (default: #t)

This Boolean indicates whether the file system needs to be checked for
errors before being mounted.

create-mount-point? (default: #f)

When true, the mount point is created if it does not exist yet.

dependencies (default: '())

This is a list of <file-system> objects representing file systems
that must be mounted before (and unmounted after) this one.

As an example, consider a hierarchy of mounts: /sys/fs/cgroup is
a dependency of /sys/fs/cgroup/cpu and
/sys/fs/cgroup/memory.

The (gnu system file-systems) exports the following useful
variables.

Scheme Variable: %base-file-systems

These are essential file systems that are required on normal systems,
such as %devtmpfs-file-system and %immutable-store (see
below.) Operating system declarations should always contain at least
these.

Scheme Variable: %devtmpfs-file-system

The devtmpfs file system to be mounted on /dev. This is a
requirement for udev (see udev-service).

Scheme Variable: %pseudo-terminal-file-system

This is the file system to be mounted as /dev/pts. It supports
pseudo-terminals created viaopenpty and similar
functions (see Pseudo-Terminals in The GNU C Library Reference
Manual). Pseudo-terminals are used by terminal emulators such as
xterm.

Scheme Variable: %shared-memory-file-system

This file system is mounted as /dev/shm and is used to support
memory sharing across processes (see shm_open in The GNU C Library Reference Manual).

Scheme Variable: %immutable-store

This file system performs a read-only “bind mount” of
/gnu/store, making it read-only for all the users including
root. This prevents against accidental modification by software
running as root or by system administrators.

The daemon itself is still able to write to the store: it remounts it
read-write in its own “name space.”

Scheme Variable: %binary-format-file-system

The binfmt_misc file system, which allows handling of arbitrary
executable file types to be delegated to user space. This requires the
binfmt.ko kernel module to be loaded.

Scheme Variable: %fuse-control-file-system

The fusectl file system, which allows unprivileged users to mount
and unmount user-space FUSE file systems. This requires the
fuse.ko kernel module to be loaded.

6.2.4 Mapped Devices

The Linux kernel has a notion of device mapping: a block device,
such as a hard disk partition, can be mapped into another device,
with additional processing over the data that flows through
it16. A
typical example is encryption device mapping: all writes to the mapped
device are encrypted, and all reads are deciphered, transparently.

This example specifies a mapping from /dev/sda3 to
/dev/mapper/home using LUKS—the
Linux Unified Key Setup, a
standard mechanism for disk encryption. The /dev/mapper/home
device can then be used as the device of a file-system
declaration (see File Systems). The mapped-device form is
detailed below.

Data Type: mapped-device

Objects of this type represent device mappings that will be made when
the system boots up.

source

This string specifies the name of the block device to be mapped, such as
"/dev/sda3".

target

This string specifies the name of the mapping to be established. For
example, specifying "my-partition" will lead to the creation of
the "/dev/mapper/my-partition" device.

type

This must be a mapped-device-kind object, which specifies how
source is mapped to target.

Scheme Variable: luks-device-mapping

This defines LUKS block device encryption using the cryptsetup
command, from the same-named package. This relies on the
dm-crypt Linux kernel module.

When booting or upon completion of guix system reconfigure,
the system ensures that only the user accounts and groups specified in
the operating-system declaration exist, and with the specified
properties. Thus, account or group creations or modifications made by
directly invoking commands such as useradd are lost upon
reconfiguration or reboot. This ensures that the system remains exactly
as declared.

Data Type: user-account

Objects of this type represent user accounts. The following members may
be specified:

name

The name of the user account.

group

This is the name (a string) or identifier (a number) of the user group
this account belongs to.

supplementary-groups (default: '())

Optionally, this can be defined as a list of group names that this
account belongs to.

uid (default: #f)

This is the user ID for this account (a number), or #f. In the
latter case, a number is automatically chosen by the system when the
account is created.

comment (default: "")

A comment about the account, such as the account’s owner full name.

home-directory

This is the name of the home directory for the account.

shell (default: Bash)

This is a G-expression denoting the file name of a program to be used as
the shell (see G-Expressions).

system? (default: #f)

This Boolean value indicates whether the account is a “system”
account. System accounts are sometimes treated specially; for instance,
graphical login managers do not list them.

password (default: #f)

You would normally leave this field to #f, initialize user
passwords as root with the passwd command, and then let
users change it with passwd. Passwords set with
passwd are of course preserved across reboot and
reconfiguration.

If you do want to have a preset password for an account, then
this field must contain the encrypted password, as a string.
See crypt in The GNU C Library Reference Manual, for more information
on password encryption, and Encryption in GNU Guile Reference
Manual, for information on Guile’s crypt procedure.

User group declarations are even simpler:

(user-group (name "students"))

Data Type: user-group

This type is for, well, user groups. There are just a few fields:

name

The group’s name.

id (default: #f)

The group identifier (a number). If #f, a new number is
automatically allocated when the group is created.

system? (default: #f)

This Boolean value indicates whether the group is a “system” group.
System groups have low numerical IDs.

password (default: #f)

What, user groups can have a password? Well, apparently yes. Unless
#f, this field specifies the group’s password.

For convenience, a variable lists all the basic user groups one may
expect:

Scheme Variable: %base-groups

This is the list of basic user groups that users and/or packages expect
to be present on the system. This includes groups such as “root”,
“wheel”, and “users”, as well as groups used to control access to
specific devices such as “audio”, “disk”, and “cdrom”.

Scheme Variable: %base-user-accounts

This is the list of basic system accounts that programs may expect to
find on a GNU/Linux system, such as the “nobody” account.

Note that the “root” account is not included here. It is a
special-case and is automatically added whether or not it is specified.

6.2.6 Locales

A locale defines cultural conventions for a particular language
and region of the world (see Locales in The GNU C Library
Reference Manual). Each locale has a name that typically has the form
language_territory.charset—e.g.,
fr_LU.utf8 designates the locale for the French language, with
cultural conventions from Luxembourg, and using the UTF-8 encoding.

Usually, you will want to specify the default locale for the machine
using the locale field of the operating-system declaration
(see locale).

That locale must be among the locale definitions that are known to
the system—and these are specified in the locale-definitions
slot of operating-system. The default value includes locale
definition for some widely used locales, but not for all the available
locales, in order to save space.

If the locale specified in the locale field is not among the
definitions listed in locale-definitions, guix system
raises an error. In that case, you should add the locale definition to
the locale-definitions field. For instance, to add the North
Frisian locale for Germany, the value of that field may be:

6.2.7 Services

An important part of preparing an operating-system declaration is
listing system services and their configuration (see Using the Configuration System). System services are typically daemons launched
when the system boots, or other actions needed at that time—e.g.,
configuring network access.

Services are managed by GNU dmd (see Introduction in GNU
dmd Manual). On a running system, the deco command allows
you to list the available services, show their status, start and stop
them, or do other specific operations (see Jump Start in GNU dmd
Manual). For example:

# deco status dmd

The above command, run as root, lists the currently defined
services. The deco doc command shows a synopsis of the given
service:

# deco doc nscd
Run libc's name service cache daemon (nscd).

The start, stop, and restart sub-commands
have the effect you would expect. For instance, the commands below stop
the nscd service and restart the Xorg display server:

# deco stop nscd
Service nscd has been stopped.
# deco restart xorg-server
Service xorg-server has been stopped.
Service xorg-server has been started.

The following sections document the available services, starting with
the core services, that may be used in an operating-system
declaration.

6.2.7.1 Base Services

The (gnu services base) module provides definitions for the basic
services that one expects from the system. The services exported by
this module are listed below.

Scheme Variable: %base-services

This variable contains a list of basic services17 one would
expect from the system: a login service (mingetty) on each tty, syslogd,
libc’s name service cache daemon (nscd), the udev device manager, and
more.

This is the default value of the services field of
operating-system declarations. Usually, when customizing a
system, you will want to append services to %base-services, like
this:

When allow-empty-passwords? is true, allow empty log-in password. When
auto-login is true, it must be a user name under which to log-in
automatically. login-pause? can be set to #t in conjunction with
auto-login, in which case the user will have to press a key before the
login shell is launched.

When true, login-program is a gexp or a monadic gexp denoting the name
of the log-in program (the default is the login program from the Shadow
tool suite.)

motd is a monadic value containing a text file to use as
the “message of the day”.

Return a service that runs libc’s name service cache daemon (nscd) with
the given config—an <nscd-configuration> object.
Optionally, #:name-services is a list of packages that provide
name service switch (NSS) modules needed by nscd. See Name Service Switch, for an example.

Scheme Variable: %nscd-default-configuration

This is the default <nscd-configuration> value (see below) used
by nscd-service. This uses the caches defined by
%nscd-default-caches; see below.

Data Type: nscd-configuration

This is the type representing the name service cache daemon (nscd)
configuration.

log-file (default: "/var/log/nscd.log")

Name of nscd’s log file. This is where debugging output goes when
debug-level is strictly positive.

This is a symbol representing the name of the database to be cached.
Valid values are passwd, group, hosts, and
services, which designate the corresponding NSS database
(see NSS Basics in The GNU C Library Reference Manual).

positive-time-to-live

negative-time-to-live (default: 20)

A number representing the number of seconds during which a positive or
negative lookup result remains in cache.

check-files? (default: #t)

Whether to check for updates of the files corresponding to
database.

For instance, when database is hosts, setting this flag
instructs nscd to check for updates in /etc/hosts and to take
them into account.

persistent? (default: #t)

Whether the cache should be stored persistently on disk.

shared? (default: #t)

Whether the cache should be shared among users.

max-database-size (default: 32 MiB)

Maximum size in bytes of the database cache.

Scheme Variable: %nscd-default-caches

List of <nscd-cache> objects used by default by
nscd-configuration (see above.)

It enables persistent and aggressive caching of service and host name
lookups. The latter provides better host name lookup performance,
resilience in the face of unreliable name servers, and also better
privacy—often the result of host name lookups is in local cache, so
external name servers do not even need to be queried.

Monadic Procedure: syslog-service[#:config-file #f]

Return a service that runs syslogd. If configuration file name
config-file is not specified, use some reasonable default
settings.

Return a service that runs BitlBee, a daemon that
acts as a gateway between IRC and chat networks.

The daemon will listen to the interface corresponding to the IP address
specified in interface, on port. 127.0.0.1 means that only
local clients can connect, whereas 0.0.0.0 means that connections can
come from any networking interface.

In addition, extra-settings specifies a string to append to the
configuration file.

Run the lshd program from lsh to listen on port port-number.
host-key must designate a file containing the host key, and readable
only by root.

When daemonic? is true, lshd will detach from the
controlling terminal and log its output to syslogd, unless one sets
syslog-output? to false. Obviously, it also makes lsh-service
depend on existence of syslogd service. When pid-file? is true,
lshd writes its PID to the file called pid-file.

When initialize? is true, automatically create the seed and host key
upon service activation if they do not exist yet. This may take long and
require interaction.

When initialize? is false, it is up to the user to initialize the
randomness generator (see lsh-make-seed in LSH Manual), and to create
a key pair with the private key stored in file host-key (see lshd
basics in LSH Manual).

When interfaces is empty, lshd listens for connections on all the
network interfaces; otherwise, interfaces must be a list of host names
or addresses.

This variable contains a string for use in /etc/hosts
(see Host Names in The GNU C Library Reference Manual). Each
line contains a entry that maps a known server name of the Facebook
on-line service—e.g., www.facebook.com—to the local
host—127.0.0.1 or its IPv6 equivalent, ::1.

This variable is typically used in the hosts-file field of an
operating-system declaration (see /etc/hosts):

6.2.7.3 X Window

Support for the X Window graphical display system—specifically
Xorg—is provided by the (gnu services xorg) module. Note that
there is no xorg-service procedure. Instead, the X server is
started by the login manager, currently SLiM.

Return a service that spawns the SLiM graphical login manager, which in
turn starts the X display server with startx, a command as returned by
xorg-start-command.

SLiM automatically looks for session types described by the .desktop
files in /run/current-system/profile/share/xsessions and allows users
to choose a session from the log-in screen using F1. Packages such as
xfce, sawfish, and ratpoison provide .desktop files;
adding them to the system-wide set of packages automatically makes them
available at the log-in screen.

In addition, ~/.xsession files are honored. When available,
~/.xsession must be an executable that starts a window manager
and/or other X clients.

When allow-empty-passwords? is true, allow logins with an empty
password. When auto-login? is true, log in automatically as
default-user.

If theme is #f, the use the default log-in theme; otherwise
theme must be a gexp denoting the name of a directory containing the
theme to use. In that case, theme-name specifies the name of the
theme.

Return a derivation that builds a guile script to start the X server
from xorg-server. configuration-file is the server configuration
file or a derivation that builds it; when omitted, the result of
xorg-configuration-file is used.

6.2.7.4 Desktop Services

The (gnu services desktop) module provides services that are
usually useful in the context of a “desktop” setup—that is, on a
machine running a graphical display server, possibly with graphical user
interfaces, etc.

To simplify things, the module defines a variable containing the set of
services that users typically expect on a machine with a graphical
environment and networking:

Scheme Variable: %desktop-services

This is a list of services that builds upon %base-services and
adds or adjust services for a typical “desktop” setup.

In particular, it adds a graphical login manager (see slim-service), a network management tool (see wicd-service), energy and color management services,
an NTP client (see Networking Services), the Avahi
daemon, and has the name service switch service configured to be able to
use nss-mdns (see mDNS).

The %desktop-services variable can be used as the services
field of an operating-system declaration (see services).

The actual service definitions provided by (gnu services desktop)
are described below.

Monadic Procedure: dbus-serviceservices [#:dbus dbus]

Return a service that runs the “system bus”, using dbus, with
support for services.

D-Bus is an inter-process communication
facility. Its system bus is used to allow system services to communicate
and be notified of system-wide events.

services must be a list of packages that provide an
etc/dbus-1/system.d directory containing additional D-Bus configuration
and policy files. For example, to allow avahi-daemon to use the system bus,
services must be equal to (list avahi).

Return a service that runs upowerd, a system-wide monitor for power consumption and battery
levels, with the given configuration settings. It implements the
org.freedesktop.UPower D-Bus interface, and is notably used by
GNOME.

Monadic Procedure: colord-service[#:colord colord]

Return a service that runs colord, a system service with a D-Bus
interface to manage the color profiles of input and output devices such as
screens and scanners. It is notably used by the GNOME Color Manager graphical
tool. See the colord web
site for more information.

6.2.8 Setuid Programs

Some programs need to run with “root” privileges, even when they are
launched by unprivileged users. A notorious example is the
passwd programs, which can users can run to change their
password, and which requires write access to the /etc/passwd and
/etc/shadow files—something normally restricted to root, for
obvious security reasons. To address that, these executables are
setuid-root, meaning that they always run with root privileges
(see How Change Persona in The GNU C Library Reference Manual,
for more info about the setuid mechanisms.)

The store itself cannot contain setuid programs: that would be a
security issue since any user on the system can write derivations that
populate the store (see The Store). Thus, a different mechanism is
used: instead of changing the setuid bit directly on files that are in
the store, we let the system administrator declare which programs
should be setuid root.

The setuid-programs field of an operating-system
declaration contains a list of G-expressions denoting the names of
programs to be setuid-root (see Using the Configuration System).
For instance, the passwd program, which is part of the Shadow
package, can be designated by this G-expression (see G-Expressions):

#~(string-append #$shadow "/bin/passwd")

A default set of setuid programs is defined by the
%setuid-programs variable of the (gnu system) module.

Scheme Variable: %setuid-programs

A list of G-expressions denoting common programs that are setuid-root.

The list includes commands such as passwd, ping,
su, and sudo.

Under the hood, the actual setuid programs are created in the
/run/setuid-programs directory at system activation time. The
files in this directory refer to the “real” binaries, which are in the
store.

6.2.9 X.509 Certificates

Web servers available over HTTPS (that is, HTTP over the transport-layer
security mechanism, TLS) send client programs an X.509 certificate
that the client can then use to authenticate the server. To do
that, clients verify that the server’s certificate is signed by a
so-called certificate authority (CA). But to verify the CA’s
signature, clients must have first acquired the CA’s certificate.

Web browsers such as GNU IceCat include their own set of CA
certificates, such that they are able to verify CA signatures
out-of-the-box.

However, most other programs that can talk HTTPS—wget,
git, w3m, etc.—need to be told where CA
certificates can be found.

In GuixSD, this is done by adding a package that provides certificates
to the packages field of the operating-system declaration
(see operating-system Reference). GuixSD includes one such package,
nss-certs, which is a set of CA certificates provided as part of
Mozilla’s Network Security Services.

Note that it is not part of %base-packages, so you need to
explicitly add it. The /etc/ssl/certs directory, which is where
most applications and libraries look for certificates by default, points
to the certificates installed globally.

Unprivileged users can also install their own certificate package in
their profile. A number of environment variables need to be defined so
that applications and libraries know where to find them. Namely, the
OpenSSL library honors the SSL_CERT_DIR and SSL_CERT_FILE
variables. Some applications add their own environment variables; for
instance, the Git version control system honors the certificate bundle
pointed to by the GIT_SSL_CAINFO environment variable.

6.2.10 Name Service Switch

The (gnu system nss) module provides bindings to the
configuration file of libc’s name service switch or NSS
(see NSS Configuration File in The GNU C Library Reference
Manual). In a nutshell, the NSS is a mechanism that allows libc to be
extended with new “name” lookup methods for system databases, which
includes host names, service names, user accounts, and more (see System Databases and Name Service Switch in The GNU
C Library Reference Manual).

The NSS configuration specifies, for each system database, which lookup
method is to be used, and how the various methods are chained
together—for instance, under which circumstances NSS should try the
next method in the list. The NSS configuration is given in the
name-service-switch field of operating-system declarations
(see name-service-switch).

As an example, the declaration below configures the NSS to use the
nss-mdns
back-end, which supports host name lookups over multicast DNS (mDNS)
for host names ending in .local:

Don’t worry: the %mdns-host-lookup-nss variable (see below)
contains this configuration, so you won’t have to type it if all you
want is to have .local host lookup working.

Note that, in this case, in addition to setting the
name-service-switch of the operating-system declaration,
nscd-service must be told where to find the nss-mdns
shared library (see nscd-service). Since the
nscd service is part of %base-services, you may want to
customize it by adding this snippet in the operating system
configuration file:

… and then refer to %my-base-services instead of
%base-services in the operating-system declaration.
Lastly, this relies on the availability of the Avahi service
(see avahi-service).

For convenience, the following variables provide typical NSS
configurations.

Scheme Variable: %default-nss

This is the default name service switch configuration, a
name-service-switch object.

Scheme Variable: %mdns-host-lookup-nss

This is the name service switch configuration with support for host name
lookup over multicast DNS (mDNS) for host names ending in .local.

The reference for name service switch configuration is given below. It
is a direct mapping of the C library’s configuration file format, so
please refer to the C library manual for more information (see NSS
Configuration File in The GNU C Library Reference Manual).
Compared to libc’s NSS configuration file format, it has the advantage
not only of adding this warm parenthetic feel that we like, but also
static checks: you’ll know about syntax errors and typos as soon as you
run guix system.

Data Type: name-service-switch

This is the data type representation the configuration of libc’s name
service switch (NSS). Each field below represents one of the supported
system databases.

aliases

ethers

group

gshadow

hosts

initgroups

netgroup

networks

password

public-key

rpc

services

shadow

The system databases handled by the NSS. Each of these fields must be a
list of <name-service> objects (see below.)

Data Type: name-service

This is the data type representing an actual name service and the
associated lookup action.

Note that name services listed here must be visible to nscd. This is
achieved by passing the #:name-services argument to
nscd-service the list of packages providing the needed name
services (see nscd-service).

6.2.11 Initial RAM Disk

For bootstrapping purposes, the Linux-Libre kernel is passed an
initial RAM disk, or initrd. An initrd contains a temporary
root file system, as well as an initialization script. The latter is
responsible for mounting the real root file system, and for loading any
kernel modules that may be needed to achieve that.

The initrd field of an operating-system declaration allows
you to specify which initrd you would like to use. The (gnu
system linux-initrd) module provides two ways to build an initrd: the
high-level base-initrd procedure, and the low-level
expression->initrd procedure.

The base-initrd procedure is intended to cover most common uses.
For example, if you want to add a bunch of kernel modules to be loaded
at boot time, you can define the initrd field of the operating
system declaration like this:

(initrd (lambda (file-systems . rest)
;; Create a standard initrd that has modules "foo.ko"
;; and "bar.ko", as well as their dependencies, in
;; addition to the modules available by default.
(apply base-initrd file-systems
#:extra-modules '("foo" "bar")
rest)))

The base-initrd procedure also handles common use cases that
involves using the system as a QEMU guest, or as a “live” system whose
root file system is volatile.

Return a monadic derivation that builds a generic initrd. file-systems is
a list of file-systems to be mounted by the initrd, possibly in addition to
the root file system specified on the kernel command line via --root.
mapped-devices is a list of device mappings to realize before
file-systems are mounted (see Mapped Devices).

When qemu-networking? is true, set up networking with the standard QEMU
parameters. When virtio? is true, load additional modules so the initrd can
be used as a QEMU guest with para-virtualized I/O drivers.

When volatile-root? is true, the root file system is writable but any changes
to it are lost.

The initrd is automatically populated with all the kernel modules necessary
for file-systems and for the given options. However, additional kernel
modules can be listed in extra-modules. They will be added to the initrd, and
loaded at boot time in the order in which they appear.

Needless to say, the initrds we produce and use embed a
statically-linked Guile, and the initialization program is a Guile
program. That gives a lot of flexibility. The
expression->initrd procedure builds such an initrd, given the
program to run in that initrd.

Return a derivation that builds a Linux initrd (a gzipped cpio archive)
containing guile and that evaluates exp, a G-expression,
upon booting. All the derivations referenced by exp are
automatically copied to the initrd.

6.2.12 GRUB Configuration

The operating system uses GNU GRUB as its boot loader
(see overview of GRUB in GNU GRUB Manual). It is
configured using grub-configuration declarations. This data type
is exported by the (gnu system grub) module, and described below.

Data Type: grub-configuration

The type of a GRUB configuration declaration.

device

This is a string denoting the boot device. It must be a device name
understood by the grub-install command, such as
/dev/sda or (hd0) (see Invoking grub-install in GNU GRUB Manual).

menu-entries (default: ())

A possibly empty list of menu-entry objects (see below), denoting
entries to appear in the GRUB boot menu, in addition to the current
system entry and the entry pointing to previous system generations.

default-entry (default: 0)

The index of the default boot menu entry. Index 0 is for the current
system’s entry.

timeout (default: 5)

The number of seconds to wait for keyboard input before booting. Set to
0 to boot immediately, and to -1 to wait indefinitely.

theme (default: %default-theme)

The grub-theme object describing the theme to use.

Should you want to list additional boot menu entries via the
menu-entries field above, you will need to create them with the
menu-entry form:

It also adds a GRUB menu entry for the new OS configuration, and moves
entries for older configurations to a submenu—unless
--no-grub is passed.

It is highly recommended to run guix pull once before you run
guix system reconfigure for the first time (see Invoking guix pull). Failing to do that you would see an older version of Guix
once reconfigure has completed.

build

Build the operating system’s derivation, which includes all the
configuration files and programs needed to boot and run the system.
This action does not actually install anything.

init

Populate the given directory with all the files necessary to run the
operating system specified in file. This is useful for first-time
installations of GuixSD. For instance:

guix system init my-os-config.scm /mnt

copies to /mnt all the store items required by the configuration
specified in my-os-config.scm. This includes configuration
files, packages, and so on. It also creates other essential files
needed for the system to operate correctly—e.g., the /etc,
/var, and /run directories, and the /bin/sh file.

This command also installs GRUB on the device specified in
my-os-config, unless the --no-grub option was passed.

vm

Build a virtual machine that contain the operating system declared in
file, and return a script to run that virtual machine (VM).
Arguments given to the script are passed as is to QEMU.

The VM shares its store with the host system.

Additional file systems can be shared between the host and the VM using
the --share and --expose command-line options: the former
specifies a directory to be shared with write access, while the latter
provides read-only access to the shared directory.

The example below creates a VM in which the user’s home directory is
accessible read-only, and where the /exchange directory is a
read-write mapping of the host’s $HOME/tmp:

On GNU/Linux, the default is to boot directly to the kernel; this has
the advantage of requiring only a very tiny root disk image since the
host’s store can then be mounted.

The --full-boot option forces a complete boot sequence, starting
with the bootloader. This requires more disk space since a root image
containing at least the kernel, initrd, and bootloader data files must
be created. The --image-size option can be used to specify the
image’s size.

vm-image

disk-image

Return a virtual machine or disk image of the operating system declared
in file that stands alone. Use the --image-size option
to specify the size of the image.

When using vm-image, the returned image is in qcow2 format, which
the QEMU emulator can efficiently use.

When using disk-image, a raw disk image is produced; it can be
copied as is to a USB stick, for instance. Assuming /dev/sdc is
the device corresponding to a USB stick, one can copy the image on it
using the following command:

# dd if=$(guix system disk-image my-os.scm) of=/dev/sdc

options can contain any of the common build options provided by
guix build (see Invoking guix build). In addition,
options can contain one of the following:

--system=system

-s system

Attempt to build for system instead of the host’s system type.
This works as per guix build (see Invoking guix build).

--image-size=size

For the vm-image and disk-image actions, create an image
of the given size. size may be a number of bytes, or it may
include a unit as a suffix (see size specifications in GNU Coreutils).

--on-error=strategy

Apply strategy when an error occurs when reading file.
strategy may be one of the following:

nothing-special

Report the error concisely and exit. This is the default strategy.

backtrace

Likewise, but also display a backtrace.

debug

Report the error and enter Guile’s debugger. From there, you can run
commands such as ,bt to get a backtrace, ,locals to
display local variable values, and more generally inspect the program’s
state. See Debug Commands in GNU Guile Reference Manual, for
a list of available debugging commands.

Note that all the actions above, except build and init,
rely on KVM support in the Linux-Libre kernel. Specifically, the
machine should have hardware virtualization support, the corresponding
KVM kernel module should be loaded, and the /dev/kvm device node
must exist and be readable and writable by the user and by the daemon’s
build users.

6.2.14 Defining Services

The (gnu services …) modules define several procedures that allow
users to declare the operating system’s services (see Using the Configuration System). These procedures are monadic
procedures—i.e., procedures that return a monadic value in the store
monad (see The Store Monad). For examples of such procedures,
See Services.

The monadic value returned by those procedures is a service
definition—a structure as returned by the service form.
Service definitions specifies the inputs the service depends on, and an
expression to start and stop the service. Behind the scenes, service
definitions are “translated” into the form suitable for the
configuration file of dmd, the init system (see Services in GNU
dmd Manual).

The activate, start, and stop fields are G-expressions
(see G-Expressions). The activate field contains a script to
run at “activation” time; it makes sure that the /var/run/nscd
directory exists before nscd is started.

The start and stop fields refer to dmd’s facilities to
start and stop processes (see Service De- and Constructors in GNU dmd Manual). The provision field specifies the name under
which this service is known to dmd, and documentation specifies
on-line documentation. Thus, the commands deco start ncsd,
deco stop nscd, and deco doc nscd will do what you
would expect (see Invoking deco in GNU dmd Manual).

6.3 Installing Debugging Files

Program binaries, as produced by the GCC compilers for instance, are
typically written in the ELF format, with a section containing
debugging information. Debugging information is what allows the
debugger, GDB, to map binary code to source code; it is required to
debug a compiled program in good conditions.

The problem with debugging information is that is takes up a fair amount
of disk space. For example, debugging information for the GNU C Library
weighs in at more than 60 MiB. Thus, as a user, keeping all the
debugging info of all the installed programs is usually not an option.
Yet, space savings should not come at the cost of an impediment to
debugging—especially in the GNU system, which should make it easier
for users to exert their computing freedom (see GNU Distribution).

Thankfully, the GNU Binary Utilities (Binutils) and GDB provide a
mechanism that allows users to get the best of both worlds: debugging
information can be stripped from the binaries and stored in separate
files. GDB is then able to load debugging information from those files,
when they are available (see Separate Debug Files in Debugging
with GDB).

The GNU distribution takes advantage of this by storing debugging
information in the lib/debug sub-directory of a separate package
output unimaginatively called debug (see Packages with Multiple Outputs). Users can choose to install the debug output
of a package when they need it. For instance, the following command
installs the debugging information for the GNU C Library and for GNU
Guile:

guix package -i glibc:debug guile:debug

GDB must then be told to look for debug files in the user’s profile, by
setting the debug-file-directory variable (consider setting it
from the ~/.gdbinit file, see Startup in Debugging with
GDB):

(gdb) set debug-file-directory ~/.guix-profile/lib/debug

From there on, GDB will pick up debugging information from the
.debug files under ~/.guix-profile/lib/debug.

In addition, you will most likely want GDB to be able to show the source
code being debugged. To do that, you will have to unpack the source
code of the package of interest (obtained with guix build
--source, see Invoking guix build), and to point GDB to that source
directory using the directory command (see directory in Debugging with GDB).

The debug output mechanism in Guix is implemented by the
gnu-build-system (see Build Systems). Currently, it is
opt-in—debugging information is available only for those packages
whose definition explicitly declares a debug output. This may be
changed to opt-out in the future, if our build farm servers can handle
the load. To check whether a package has a debug output, use
guix package --list-available (see Invoking guix package).

6.4 Security Updates

Note: As of version 0.8.3, the feature described in this section is
experimental.

Occasionally, important security vulnerabilities are discovered in core
software packages and must be patched. Guix follows a functional
package management discipline (see Introduction), which implies
that, when a package is changed, every package that depends on it
must be rebuilt. This can significantly slow down the deployment of
fixes in core packages such as libc or Bash, since basically the whole
distribution would need to be rebuilt. Using pre-built binaries helps
(see Substitutes), but deployment may still take more time than
desired.

To address that, Guix implements grafts, a mechanism that allows
for fast deployment of critical updates without the costs associated
with a whole-distribution rebuild. The idea is to rebuild only the
package that needs to be patched, and then to “graft” it onto packages
explicitly installed by the user and that were previously referring to
the original package. The cost of grafting is typically very low, and
order of magnitudes lower than a full rebuild of the dependency chain.

For instance, suppose a security update needs to be applied to Bash.
Guix developers will provide a package definition for the “fixed”
Bash, say bash-fixed, in the usual way (see Defining Packages). Then, the original package definition is augmented with a
replacement field pointing to the package containing the bug fix:

(define bash
(package
(name "bash")
;; …
(replacement bash-fixed)))

From there on, any package depending directly or indirectly on Bash that
is installed will automatically be “rewritten” to refer to
bash-fixed instead of bash. This grafting process takes
time proportional to the size of the package, but expect less than a
minute for an “average” package on a recent machine.

Currently, the graft and the package it replaces (bash-fixed and
bash in the example above) must have the exact same name
and version fields. This restriction mostly comes from the fact
that grafting works by patching files, including binary files, directly.
Other restrictions may apply: for instance, when adding a graft to a
package providing a shared library, the original shared library and its
replacement must have the same SONAME and be binary-compatible.

6.5 Package Modules

From a programming viewpoint, the package definitions of the
GNU distribution are provided by Guile modules in the (gnu packages
…) name space19 (see Guile modules in GNU Guile
Reference Manual). For instance, the (gnu packages emacs)
module exports a variable named emacs, which is bound to a
<package> object (see Defining Packages).

The (gnu packages …) module name space is
automatically scanned for packages by the command-line tools. For
instance, when running guix package -i emacs, all the (gnu
packages …) modules are scanned until one that exports a package
object whose name is emacs is found. This package search
facility is implemented in the (gnu packages) module.

Users can store package definitions in modules with different
names—e.g., (my-packages emacs)20. These package definitions
will not be visible by default. Thus, users can invoke commands such as
guix package and guix build have to be used with the
-e option so that they know where to find the package. Better
yet, they can use the
-L option of these commands to make those modules visible
(see --load-path), or define the
GUIX_PACKAGE_PATH environment variable. This environment
variable makes it easy to extend or customize the distribution and is
honored by all the user interfaces.

Environment Variable: GUIX_PACKAGE_PATH

This is a colon-separated list of directories to search for package
modules. Directories listed in this variable take precedence over the
distribution’s own modules.

The distribution is fully bootstrapped and self-contained:
each package is built based solely on other packages in the
distribution. The root of this dependency graph is a small set of
bootstrap binaries, provided by the (gnu packages
bootstrap) module. For more information on bootstrapping,
see Bootstrapping.

6.6 Packaging Guidelines

The GNU distribution is nascent and may well lack some of your favorite
packages. This section describes how you can help make the distribution
grow. See Contributing, for additional information on how you can
help.

Free software packages are usually distributed in the form of
source code tarballs—typically tar.gz files that contain
all the source files. Adding a package to the distribution means
essentially two things: adding a recipe that describes how to
build the package, including a list of other packages required to build
it, and adding package meta-data along with that recipe, such as a
description and licensing information.

In Guix all this information is embodied in package definitions.
Package definitions provide a high-level view of the package. They are
written using the syntax of the Scheme programming language; in fact,
for each package we define a variable bound to the package definition,
and export that variable from a module (see Package Modules).
However, in-depth Scheme knowledge is not a prerequisite for
creating packages. For more information on package definitions,
see Defining Packages.

Once a package definition is in place, stored in a file in the Guix
source tree, it can be tested using the guix build command
(see Invoking guix build). For example, assuming the new package is
called gnew, you may run this command from the Guix build tree
(see Running Guix Before It Is Installed):

./pre-inst-env guix build gnew --keep-failed

Using --keep-failed makes it easier to debug build failures since
it provides access to the failed build tree. Another useful
command-line option when debugging is --log-file, to access the
build log.

If the package is unknown to the guix command, it may be that
the source file contains a syntax error, or lacks a define-public
clause to export the package variable. To figure it out, you may load
the module from Guile to get more information about the actual error:

./pre-inst-env guile -c '(use-modules (gnu packages gnew))'

Once your package builds correctly, please send us a patch
(see Contributing). Well, if you need help, we will be happy to
help you too. Once the patch is committed in the Guix repository, the
new package automatically gets built on the supported platforms by
our continuous integration
system.

Users can obtain the new package definition simply by running
guix pull (see Invoking guix pull). When
hydra.gnu.org is done building the package, installing the
package automatically downloads binaries from there
(see Substitutes). The only place where human intervention is
needed is to review and apply the patch.

6.6.1 Software Freedom

The GNU operating system has been developed so that users can have
freedom in their computing. GNU is free software, meaning that
users have the four
essential freedoms: to run the program, to study and change the program
in source code form, to redistribute exact copies, and to distribute
modified versions. Packages found in the GNU distribution provide only
software that conveys these four freedoms.

In addition, the GNU distribution follow the
free
software distribution guidelines. Among other things, these guidelines
reject non-free firmware, recommendations of non-free software, and
discuss ways to deal with trademarks and patents.

Some packages contain a small and optional subset that violates the
above guidelines, for instance because this subset is itself non-free
code. When that happens, the offending items are removed with
appropriate patches or code snippets in the package definition’s
origin form (see Defining Packages). That way, guix
build --source returns the “freed” source rather than the unmodified
upstream source.

6.6.2 Package Naming

A package has actually two names associated with it:
First, there is the name of the Scheme variable, the one following
define-public. By this name, the package can be made known in the
Scheme code, for instance as input to another package. Second, there is
the string in the name field of a package definition. This name
is used by package management commands such as
guix package and guix build.

Both are usually the same and correspond to the lowercase conversion of
the project name chosen upstream, with underscores replaced with
hyphens. For instance, GNUnet is available as gnunet, and
SDL_net as sdl-net.

We do not add lib prefixes for library packages, unless these are
already part of the official project name. But see Python Modules and Perl Modules for special rules concerning modules for
the Python and Perl languages.

6.6.3 Version Numbers

We usually package only the latest version of a given free software
project. But sometimes, for instance for incompatible library versions,
two (or more) versions of the same package are needed. These require
different Scheme variable names. We use the name as defined
in Package Naming
for the most recent version; previous versions use the same name, suffixed
by - and the smallest prefix of the version number that may
distinguish the two versions.

The name inside the package definition is the same for all versions of a
package and does not contain any version number.

For instance, the versions 2.24.20 and 3.9.12 of GTK+ may be packaged as follows:

6.6.4 Python Modules

We currently package Python 2 and Python 3, under the Scheme variable names
python-2 and python as explained in Version Numbers.
To avoid confusion and naming clashes with other programming languages, it
seems desirable that the name of a package for a Python module contains
the word python.

Some modules are compatible with only one version of Python, others with both.
If the package Foo compiles only with Python 3, we name it
python-foo; if it compiles only with Python 2, we name it
python2-foo. If it is compatible with both versions, we create two
packages with the corresponding names.

If a project already contains the word python, we drop this;
for instance, the module python-dateutil is packaged under the names
python-dateutil and python2-dateutil.

6.6.5 Perl Modules

Perl programs standing for themselves are named as any other package,
using the lowercase upstream name.
For Perl packages containing a single class, we use the lowercase class name,
replace all occurrences of :: by dashes and prepend the prefix
perl-.
So the class XML::Parser becomes perl-xml-parser.
Modules containing several classes keep their lowercase upstream name and
are also prepended by perl-. Such modules tend to have the word
perl somewhere in their name, which gets dropped in favor of the
prefix. For instance, libwww-perl becomes perl-libwww.

6.6.6 Fonts

For fonts that are in general not installed by a user for typesetting
purposes, or that are distributed as part of a larger software package,
we rely on the general packaging rules for software; for instance, this
applies to the fonts delivered as part of the X.Org system or fonts that
are part of TeX Live.

To make it easier for a user to search for fonts, names for other packages
containing only fonts are constructed as follows, independently of the
upstream package name.

The name of a package containing only one font family starts with
font-; it is followed by the foundry name and a dash -
if the foundry is known, and the font family name, in which spaces are
replaced by dashes (and as usual, all upper case letters are transformed
to lower case).
For example, the Gentium font family by SIL is packaged under the name
font-sil-gentium.

For a package containing several font families, the name of the collection
is used in the place of the font family name.
For instance, the Liberation fonts consist of three families,
Liberation Sans, Liberation Serif and Liberation Mono.
These could be packaged separately under the names
font-liberation-sans and so on; but as they are distributed together
under a common name, we prefer to package them together as
font-liberation.

In the case where several formats of the same font family or font collection
are packaged separately, a short form of the format, prepended by a dash,
is added to the package name. We use -ttf for TrueType fonts,
-otf for OpenType fonts and -type1 for PostScript Type 1
fonts.

6.7 Bootstrapping

Bootstrapping in our context refers to how the distribution gets built
“from nothing”. Remember that the build environment of a derivation
contains nothing but its declared inputs (see Introduction). So
there’s an obvious chicken-and-egg problem: how does the first package
get built? How does the first compiler get compiled? Note that this is
a question of interest only to the curious hacker, not to the regular
user, so you can shamelessly skip this section if you consider yourself
a “regular user”.

The GNU system is primarily made of C code, with libc at its core. The
GNU build system itself assumes the availability of a Bourne shell and
command-line tools provided by GNU Coreutils, Awk, Findutils, ‘sed’, and
‘grep’. Furthermore, build programs—programs that run
./configure, make, etc.—are written in Guile Scheme
(see Derivations). Consequently, to be able to build anything at
all, from scratch, Guix relies on pre-built binaries of Guile, GCC,
Binutils, libc, and the other packages mentioned above—the
bootstrap binaries.

These bootstrap binaries are “taken for granted”, though we can also
re-create them if needed (more on that later).

Preparing to Use the Bootstrap Binaries

The figure above shows the very beginning of the dependency graph of the
distribution, corresponding to the package definitions of the (gnu
packages bootstrap) module. At this level of detail, things are
slightly complex. First, Guile itself consists of an ELF executable,
along with many source and compiled Scheme files that are dynamically
loaded when it runs. This gets stored in the guile-2.0.7.tar.xz
tarball shown in this graph. This tarball is part of Guix’s “source”
distribution, and gets inserted into the store with add-to-store
(see The Store).

But how do we write a derivation that unpacks this tarball and adds it
to the store? To solve this problem, the guile-bootstrap-2.0.drv
derivation—the first one that gets built—uses bash as its
builder, which runs build-bootstrap-guile.sh, which in turn calls
tar to unpack the tarball. Thus, bash, tar,
xz, and mkdir are statically-linked binaries, also part of
the Guix source distribution, whose sole purpose is to allow the Guile
tarball to be unpacked.

Once guile-bootstrap-2.0.drv is built, we have a functioning
Guile that can be used to run subsequent build programs. Its first task
is to download tarballs containing the other pre-built binaries—this
is what the .tar.xz.drv derivations do. Guix modules such as
ftp-client.scm are used for this purpose. The
module-import.drv derivations import those modules in a directory
in the store, using the original layout. The
module-import-compiled.drv derivations compile those modules, and
write them in an output directory with the right layout. This
corresponds to the #:modules argument of
build-expression->derivation (see Derivations).

Finally, the various tarballs are unpacked by the
derivations gcc-bootstrap-0.drv, glibc-bootstrap-0.drv,
etc., at which point we have a working C tool chain.

Building the Build Tools

Bootstrapping is complete when we have a full tool chain that does not
depend on the pre-built bootstrap tools discussed above. This
no-dependency requirement is verified by checking whether the files of
the final tool chain contain references to the /gnu/store
directories of the bootstrap inputs. The process that leads to this
“final” tool chain is described by the package definitions found in
the (gnu packages commencement) module.

The first tool that gets built with the bootstrap binaries is
GNU Make, which is a prerequisite for all the following packages.
From there Findutils and Diffutils get built.

Then come the first-stage Binutils and GCC, built as pseudo cross
tools—i.e., with --target equal to --host. They are
used to build libc. Thanks to this cross-build trick, this libc is
guaranteed not to hold any reference to the initial tool chain.

From there the final Binutils and GCC are built. GCC uses ld
from the final Binutils, and links programs against the just-built libc.
This tool chain is used to build the other packages used by Guix and by
the GNU Build System: Guile, Bash, Coreutils, etc.

And voilà! At this point we have the complete set of build tools that
the GNU Build System expects. These are in the %final-inputs
variable of the (gnu packages commencement) module, and are
implicitly used by any package that uses gnu-build-system
(see gnu-build-system).

Building the Bootstrap Binaries

Because the final tool chain does not depend on the bootstrap binaries,
those rarely need to be updated. Nevertheless, it is useful to have an
automated way to produce them, should an update occur, and this is what
the (gnu packages make-bootstrap) module provides.

The following command builds the tarballs containing the bootstrap
binaries (Guile, Binutils, GCC, libc, and a tarball containing a mixture
of Coreutils and other basic command-line tools):

guix build bootstrap-tarballs

The generated tarballs are those that should be referred to in the
(gnu packages bootstrap) module mentioned at the beginning of
this section.

Still here? Then perhaps by now you’ve started to wonder: when do we
reach a fixed point? That is an interesting question! The answer is
unknown, but if you would like to investigate further (and have
significant computational and storage resources to do so), then let us
know.

6.8 Porting to a New Platform

As discussed above, the GNU distribution is self-contained, and
self-containment is achieved by relying on pre-built “bootstrap
binaries” (see Bootstrapping). These binaries are specific to an
operating system kernel, CPU architecture, and application binary
interface (ABI). Thus, to port the distribution to a platform that is
not yet supported, one must build those bootstrap binaries, and update
the (gnu packages bootstrap) module to use them on that platform.

Fortunately, Guix can cross compile those bootstrap binaries.
When everything goes well, and assuming the GNU tool chain supports the
target platform, this can be as simple as running a command like this
one:

guix build --target=armv5tel-linux-gnueabi bootstrap-tarballs

For this to work, the glibc-dynamic-linker procedure in
(gnu packages bootstrap) must be augmented to return the right
file name for libc’s dynamic linker on that platform; likewise,
system->linux-architecture in (gnu packages linux) must be
taught about the new platform.

Once these are built, the (gnu packages bootstrap) module needs
to be updated to refer to these binaries on the target platform. That
is, the hashes and URLs of the bootstrap tarballs for the new platform
must be added alongside those of the currently supported platforms. The
bootstrap Guile tarball is treated specially: it is expected to be
available locally, and gnu-system.am has rules do download it for
the supported architectures; a rule for the new platform must be added
as well.

In practice, there may be some complications. First, it may be that the
extended GNU triplet that specifies an ABI (like the eabi suffix
above) is not recognized by all the GNU tools. Typically, glibc
recognizes some of these, whereas GCC uses an extra --with-abi
configure flag (see gcc.scm for examples of how to handle this).
Second, some of the required packages could fail to build for that
platform. Lastly, the generated binaries could be broken for some
reason.

7 Contributing

This project is a cooperative effort, and we need your help to make it
grow! Please get in touch with us on guix-devel@gnu.org and
#guix on the Freenode IRC network. We welcome ideas, bug
reports, patches, and anything that may be helpful to the project. We
particularly welcome help on packaging (see Packaging Guidelines).

7.1 Building from Git

If you want to hack Guix itself, it is recommended to use the latest
version from the Git repository. When building Guix from a checkout,
the following packages are required in addition to those mentioned in
the installation instructions (see Requirements).

Run ./bootstrap to download the Nix daemon source code and to
generate the build system infrastructure using autoconf. It reports an
error if an inappropriate version of the above packages is being used.

If you get an error like this one:

configure.ac:46: error: possibly undefined macro: PKG_CHECK_MODULES

it probably means that Autoconf couldn’t find pkg.m4, which is
provided by pkg-config. Make sure that pkg.m4 is
available. For instance, if you installed Automake in
/usr/local, it wouldn’t look for .m4 files in
/usr/share. So you have to invoke the following command in that
case

7.2 Running Guix Before It Is Installed

In order to keep a sane working environment, you will find it useful to
test the changes made in your local source tree checkout without
actually installing them. So that you can distinguish between your
“end-user” hat and your “motley” costume.

To that end, all the command-line tools can be used even if you have not
run make install. To do that, prefix each command with
./pre-inst-env (the pre-inst-env script lives in the
top build tree of Guix), as in:

7.3 The Perfect Setup

The Perfect Setup to hack on Guix is basically the perfect setup used
for Guile hacking (see Using Guile in Emacs in Guile Reference
Manual). First, you need more than an editor, you need
Emacs, empowered by the
wonderful Geiser.

Geiser allows for interactive and incremental development from within
Emacs: code compilation and evaluation from within buffers, access to
on-line documentation (docstrings), context-sensitive completion,
M-. to jump to an object definition, a REPL to try out your code,
and more (see Introduction in Geiser User Manual). For
convenient Guix development, make sure to augment Guile’s load path so
that it finds source files from your checkout:

To actually edit the code, Emacs already has a neat Scheme mode. But in
addition to that, you must not miss
Paredit. It provides
facilities to directly operate on the syntax tree, such as raising an
s-expression or wrapping it, swallowing or rejecting the following
s-expression, etc.

7.4.2 Modules

Guile modules that are meant to be used on the builder side must live in
the (guix build …) name space. They must not refer to
other Guix or GNU modules. However, it is OK for a “host-side” module
to use a build-side module.

Modules that deal with the broader GNU system should be in the
(gnu …) name space rather than (guix …).

7.4.3 Data Types and Pattern Matching

The tendency in classical Lisp is to use lists to represent everything,
and then to browse them “by hand” using car, cdr,
cadr, and co. There are several problems with that style,
notably the fact that it is hard to read, error-prone, and a hindrance
to proper type error reports.

7.4.4 Formatting Code

When writing Scheme code, we follow common wisdom among Scheme
programmers. In general, we follow the
Riastradh’s Lisp
Style Rules. This document happens to describe the conventions mostly
used in Guile’s code too. It is very thoughtful and well written, so
please do read it.

Some special forms introduced in Guix, such as the substitute*
macro, have special indentation rules. These are defined in the
.dir-locals.el file, which Emacs automatically uses. If you do
not use Emacs, please make sure to let your editor know the rules.

We require all top-level procedures to carry a docstring. This
requirement can be relaxed for simple private procedures in the
(guix build …) name space, though.

Procedures should not have more than four positional parameters. Use
keyword parameters for procedures that take more than four parameters.

7.5 Submitting Patches

Development is done using the Git distributed version control system.
Thus, access to the repository is not strictly necessary. We welcome
contributions in the form of patches as produced by git
format-patch sent to the mailing list.
Please write commit logs in the ChangeLog format (see Change Logs in GNU Coding Standards); you can check the commit history for
examples.

Before submitting a patch that adds or modifies a package definition,
please run through this check list:

Run guix lint package, where package is the
name of the new or modified package, and fix any errors it reports
(see Invoking guix lint).

Make sure the package builds on your platform, using guix build
package.

Take a look at the profile reported by guix size
(see Invoking guix size). This will allow you to notice references
to other packages unwillingly retained. It may also help determine
whether to split the package (see Packages with Multiple Outputs),
and which optional dependencies should be used.

For important changes, check that dependent package (if applicable) are
not affected by the change; guix refresh --list-dependent
package will help you do that (see Invoking guix refresh).

When posting a patch to the mailing list, use ‘[PATCH] …’ as a
subject. You may use your email client or the git send-mail
command.

8 Acknowledgments

Guix is based on the Nix package manager, which was designed and
implemented by Eelco Dolstra, with contributions from other people (see
the nix/AUTHORS file in Guix.) Nix pioneered functional package
management, and promoted unprecedented features, such as transactional
package upgrades and rollbacks, per-user profiles, and referentially
transparent build processes. Without this work, Guix would not exist.

The Nix-based software distributions, Nixpkgs and NixOS, have also been
an inspiration for Guix.

GNU Guix itself is a collective work with contributions from a
number of people. See the AUTHORS file in Guix for more
information on these fine people. The THANKS file lists people
who have helped by reporting bugs, taking care of the infrastructure,
providing artwork and themes, making suggestions, and more—thank you!

The purpose of this License is to make a manual, textbook, or other
functional and useful document free in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.

This License is a kind of “copyleft”, which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft
license designed for free software.

We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License
principally for works whose purpose is instruction or reference.

APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License. Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein. The “Document”, below,
refers to any such manual or work. Any member of the public is a
licensee, and is addressed as “you”. You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.

A “Modified Version” of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.

A “Secondary Section” is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document’s overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject. (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.

The “Invariant Sections” are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License. If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant. The Document may contain zero
Invariant Sections. If the Document does not identify any Invariant
Sections then there are none.

The “Cover Texts” are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License. A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.

A “Transparent” copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters. A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text. A copy that is not “Transparent” is called “Opaque”.

Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input
format, SGML or XML using a publicly available
DTD, and standard-conforming simple HTML,
PostScript or PDF designed for human modification. Examples
of transparent image formats include PNG, XCF and
JPG. Opaque formats include proprietary formats that can be
read and edited only by proprietary word processors, SGML or
XML for which the DTD and/or processing tools are
not generally available, and the machine-generated HTML,
PostScript or PDF produced by some word processors for
output purposes only.

The “Title Page” means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page. For works in
formats which do not have any title page as such, “Title Page” means
the text near the most prominent appearance of the work’s title,
preceding the beginning of the body of the text.

The “publisher” means any person or entity that distributes copies
of the Document to the public.

A section “Entitled XYZ” means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language. (Here XYZ stands for a
specific section name mentioned below, such as “Acknowledgements”,
“Dedications”, “Endorsements”, or “History”.) To “Preserve the Title”
of such a section when you modify the Document means that it remains a
section “Entitled XYZ” according to this definition.

The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.

VERBATIM COPYING

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and
you may publicly display copies.

COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document’s license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify
you as the publisher of these copies. The front cover must present
the full title with all words of the title equally prominent and
visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.

It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.

MODIFICATIONS

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it. In addition, you must do these things in the Modified Version:

Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document). You may use the same title as a previous version
if the original publisher of that version gives permission.

List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.

State on the Title page the name of the publisher of the
Modified Version, as the publisher.

Preserve all the copyright notices of the Document.

Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.

Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.

Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document’s license notice.

Include an unaltered copy of this License.

Preserve the section Entitled “History”, Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page. If
there is no section Entitled “History” in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.

Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the “History” section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.

For any section Entitled “Acknowledgements” or “Dedications”, Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.

Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.

Delete any section Entitled “Endorsements”. Such a section
may not be included in the Modified Version.

Do not retitle any existing section to be Entitled “Endorsements” or
to conflict in title with any Invariant Section.

Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version’s license notice.
These titles must be distinct from any other section titles.

You may add a section Entitled “Endorsements”, provided it contains
nothing but endorsements of your Modified Version by various
parties—for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.

COMBINING DOCUMENTS

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled “History”
in the various original documents, forming one section Entitled
“History”; likewise combine any sections Entitled “Acknowledgements”,
and any sections Entitled “Dedications”. You must delete all
sections Entitled “Endorsements.”

COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.

AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an “aggregate” if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation’s users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document’s Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.

TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers. In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.

If a section in the Document is Entitled “Acknowledgements”,
“Dedications”, or “History”, the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.

TERMINATION

You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.

Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.

Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.

FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License “or any later version” applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation. If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy’s public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.

RELICENSING

“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server. A
“Massive Multiauthor Collaboration” (or “MMC”) contained in the
site means any set of copyrightable works thus published on the MMC
site.

“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.

“Incorporate” means to publish or republish a Document, in whole or
in part, as part of another Document.

An MMC is “eligible for relicensing” if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

Copyright (C) yearyour name.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the “with…Texts.” line with this:

with the Invariant Sections being list their titles, with
the Front-Cover Texts being list, and with the Back-Cover Texts
being list.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.

The term stratum in this context was coined by
Manuel Serrano et al. in the context of their work on Hop. Oleg
Kiselyov, who has written insightful
essays and code
on this topic, refers to this kind of code generation as
staging.

Users sometimes wrongfully augment
environment variables such as PATH in their ~/.bashrc
file. As a consequence, when guix environment launches it, Bash
may read ~/.bashrc, thereby introducing “impurities” in these
environment variables. It is an error to define such environment
variables in .bashrc; instead, they should be defined in
.bash_profile, which is sourced only by log-in shells.
See Bash Startup Files in The GNU Bash Reference Manual, for
details on Bash start-up files.

The name eno1 is for the first on-board Ethernet controller. The
interface name for an Ethernet controller that is in the first slot of
the first PCI bus, for instance, would be enp1s0. Use
ifconfig -a to list all the available network interfaces.

Note that, while it is tempting to use
/dev/disk/by-uuid and similar device names to achieve the same
result, this is not recommended: These special device nodes are created
by the udev daemon and may be unavailable at the time the device is
mounted.

Note that the GNU Hurd makes no difference between the
concept of a “mapped device” and that of a file system: both boil down
to translating input/output operations made on a file to
operations on its backing store. Thus, the Hurd implements mapped
devices, like file systems, using the generic translator mechanism
(see Translators in The GNU Hurd Reference Manual).

Note that packages under the (gnu
packages …) module name space are not necessarily “GNU
packages”. This module naming scheme follows the usual Guile module
naming convention: gnu means that these modules are distributed
as part of the GNU system, and packages identifies modules that
define packages.

Note that the file
name and module name must match. For instance, the (my-packages
emacs) module must be stored in a my-packages/emacs.scm file
relative to the load path specified with --load-path or
GUIX_PACKAGE_PATH. See Modules and the File System in GNU Guile Reference Manual, for details.